Effects and Mechanisms of Tastants on the Gustatory ...downloads.hindawi.com/journals/bmri/2018/3847075.pdf · ResearchArticle Effects and Mechanisms of Tastants on the Gustatory-Salivary

Research ArticleEffects and Mechanisms of Tastants on the Gustatory-SalivaryReflex in Human Minor Salivary Glands

Shizuko Satoh-Kuriwada Noriaki Shoji Hiroyuki MiyakeChiyoWatanabe and Takashi Sasano

Division of Oral Diagnosis Department of Oral Medicine and Surgery Tohoku University Graduate School of Dentistry4-1 Seiryo-machi Aoba-ku Sendai 980-8575 Japan

Correspondence should be addressed to Shizuko Satoh-Kuriwada kuri-shudenttohokuacjp

Received 20 October 2017 Accepted 26 December 2017 Published 31 January 2018

Academic Editor Elsa Lamy

Copyright copy 2018 Shizuko Satoh-Kuriwada et alThis is an open access article distributed under the Creative CommonsAttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

The effects and mechanisms of tastes on labial minor salivary gland (LMSG) secretion were investigated in 59 healthy individualsStimulation with each of the five basic tastes (ie sweet salty sour bitter and umami) onto the tongue induced LMSG secretion in adose-dependentmanner Umami and sour tastes evoked greater secretion than did the other tastes A synergistic effect of umami onLMSG secretion was recognized a much greater increase in secretion was observed by a mixed solution of monosodium glutamateand inosine 51015840-monophosphate than by each separate stimulation Blood flow (BF) in the nearby labial mucosa also increasedfollowing stimulation by each taste except bitter The BF change and LMSG secretion in each participant showed a significantpositive correlationwith all tastes including bitter Administration of cevimeline hydrochloride hydrate to the labialmucosa evokeda significant increase in both LMSG secretion and BF while adrenaline atropine and pirenzepine decreased LMSG secretion andBFThe change in LMSG secretion and BF induced by each autonomic agent was significantly correlated in each participant Theseresults indicate that basic tastes can induce the gustatory-salivary reflex in human LMSGs and that parasympathetic regulation isinvolved in this mechanism

1 Introduction

Theminor salivary glands are vital for themaintenance of oralhealth because they secrete abundant mucin which acts asa lubricant [1] and are involved in immunoactivity throughsecretion of immunoglobulin A [2] Although the minorsalivary glands contain less volume than the major salivaryglands [3] they are widely distributed throughout the oralmucosa [4]

Eating is a strong stimulus for the secretion of saliva bythe major salivary glands [5] Large volumes of saliva aresecreted before during and after eating via the gustatory-salivary reflex masticatory-salivary reflex olfactory-salivaryreflex and esophageal-salivary reflex Parasympathetic effer-ent activities induced by taste stimuli have been shown toinvolve salivation and vasodilation in the major salivaryglands [6] However the details of secretion mechanismsin the minor salivary glands remain unclear because ofdifficulties in collecting and quantifying the minute secretion

volume from the minor salivary glands We previously devel-oped a new technique formeasuring theminor salivary glandflow using a simple iodine-starch filter paper method [7] anddemonstrated that the subjective feeling of dry mouth wasmore strongly related to a reduction in minor salivary glandflow than in whole salivary flow [8] This finding suggests animportant role of the minor salivary glands in xerostomia

In the present study we examined the effects of fivebasic taste stimuli (sweet salty sour bitter and umami) onreflex salivation in the human labial minor salivary glands(LMSGs) Specifically we studied the synergistic effect of theumami taste on reflexive LMSG secretion because the com-bined umami taste of monosodium glutamate (MSG) andinosine 51015840-monophosphate (IMP) is widely known to havea strong effect on taste perception as a characteristic featureof the umami taste [9] Additionally we investigated thenervous control of LMSG secretion using autonomic agentswhile monitoring the nearby blood flow (BF) in the labialmucosa where LMSG secretion was observed

HindawiBioMed Research InternationalVolume 2018 Article ID 3847075 12 pageshttpsdoiorg10115520183847075

2 BioMed Research International

2 Materials and Methods

21 Participants and Exclusion Criteria In total 64 healthyparticipants were initially recruited from the students atTohoku University and the residents and staff membersat Tohoku University Hospital Individuals with systemicdisease (eg endocrine infectious or immunological diseaseor a history of chemotherapy andor radiation therapy forhead and neck cancer) who had been prescribed medi-cations that could directly affect dry mouth or who hada feeling of oral dryness were excluded Individuals withhyposalivation identified by measuring the LMSG flow andthose with a history of psychological problems were alsoexcluded after careful interviews and psychological testing(Self-Rating Depression Scale) to avoid psychogenic oraldryness Consequently 56 individuals (average age 312plusmn83years age range 19ndash42 years 44 men 12 women) were finallyincludedThese participants were divided into four groups toevaluate the LMSG responses to taste (119899 = 21) the synergisticeffect of umami (119899 = 10) the relationship between LMSGsecretion and the BF change where the LMSG are located(119899 = 14) and the involvement of the autonomic nervoussystem in LMSG secretion and the BF change (119899 = 11) Thisstudy was designed and conducted in complete accordancewith the World Medical Association Declaration of Helsinki(httpwwwwmanet) and was approved by the Ethics Com-mittee of the Tohoku University Graduate School of Den-tistry Written consent was obtained from each participantafter they had received an explanation of the purpose of thestudy

22 Quantification of LMSG Secretion The LMSG secretionresponses to distilled water (DW) tastants or autonomicagents were quantified using the iodine-starch filter papermethod as previously described [7] Briefly a strip of testpaper (3 times 1 cm Filter paper 1 Toyo Roshi Kaisha LtdTokyo Japan) painted with a solution of iodine in absolutealcohol and a fine starch powder mixed with castor oil wasapplied onto the lower lip for 2min [7]Theblackened areas ofeach test paper imprinted by the iodine-starch reaction werescanned and digitized at 8 bits using a GT-9500 ART imagescanner (Seiko Epson Corp Nagoya Japan) with the scan-ning resolution set at 144 dpi The total area was measuredusing image analysis software (Scion Image Beta 402 ScionCorporation Frederick MD USA) Each total area value wasconverted to a flow rate (120583Lcm2min) using the calibrationline119884 = minus0084+24992119883 (119884 area inmm2119883 volume in 120583L)previously described [7]

23 BF Measurements in Labial Mucosa BF changes in thelower labial mucosa where quantification of the LMSGsecretion was undertaken were continuously monitoredusing reflection-mode laser Doppler flowmetry (SNF12007Cyber Firm Med Inc Tokyo Japan) before and after theadministration of DW tastants or autonomic agents Duringmeasurement of the BF the participants were asked to keeptheir mouths open and the lower lip was everted using anangle widener The test areas were isolated with rolled gauzeand then dried with a cotton gauze pad immediately before

the recording was performed A sensor probe was firmlyanchored to the angle widener with surgical tape and thetip of the probe was kept at a distance of 05mm from thelip surface All recordings were electrically calibrated to zeroBF Laser Doppler signals from the lower labial mucosa werecontinuously monitored together with the systemic bloodpressure (BP) (Finometer Finapres Medical Systems Ams-terdam Netherlands) The outputs from the flowmeter andBP monitor were recorded on a multichannel chart recorder(Recti-Horiz-8K NEC San-ei Tokyo Japan)

24 Taste Stimulation

241 Five Basic Tastes Five well-established taste substanceswere used For the four basic tastes (sweet salty sour andbitter) ready-made test solutions of Taste Disc (SanwaChemical Co Ltd Nagoya Japan) were used Each concen-tration of the four basic tastes was as follows

(i) Sweet (sucrose) 87mM (No 1 S1) 730mM (No 2S2) 2921mM (No 3 S3) 5842mM (No 4 S4) and23371mM (No 5 S5)

(ii) Salty (NaCl) 513mM (No 1 N1) 2138mM (No 2N2) 8555mM(No 3N3) 17111mM(No 4N4) and34223mM (No 5 N5)

(iii) Sour (tartaric acid) 13mM (No 1 T1) 133mM (No2 T2) 1332mM (No 3 T3) 2665mM (No 4 T4)and 5330mM (No 5 T5)

(iv) Bitter (quinine) 003mM (No 1 Q1) 05mM (No 2Q2) 25mM (No 3 Q3) 126mM (No 4 Q4) and1007mM (No 5 Q5)

For umami tasteMSGaqueous solution previously devel-oped for an umami taste sensitivity test [10] was used Theconcentrations of the umami taste were 1mM (No 1 G1)5mM (No 2 G2) 10mM (No 3 G3) 50mM (No 4 G4) and100mM (No 5 G5) Each taste number (Nos 1ndash5) was set upso that the intensity of the participantrsquos perception of the tastewas equivalent in spite of the different taste qualities basedon previously reported data of the Taste Disc [11] and ourpreviously described findings regarding umami [10] Thusthe intensity of perception of the same taste number (Nos1ndash5) was equal among the five tastes

A 5mm diameter cotton ball containing 50 120583L of eachtaste solution or DW was applied onto the posterior tonguefor 2min and the LMSG secretion was then measured Theparticipants were asked to rinse their mouth with water forat least 15min between each taste stimulation The next tastestimulation was applied after the measurement value hadreturned to the baseline level All participants (119899 = 21)were asked to refrain from eating or drinking (except water)smoking and brushing their teeth for at least 3 h beforetesting

242 Combined Umami Tastes of MSG and IMP To inves-tigate the well-known synergistic effect of combined umamitastes on LMSG secretion 5mM of MSG aqueous solution5mM of IMP aqueous solution and a solution containinga mixture of the two (5mM MSG and 5mM IMP) were

BioMed Research International 3

prepared Combined umami tastes that have been shown toevoke a synergistic effect [9] were made using an aqueoussolution containing 10mM MSG and 10mM IMP Changesin LMSG secretion were quantified following each admin-istration of MSG IMP or MSG + IMP solution onto theposterior tongue of 10 participantsTheprocedurewas similarto the above-described experiment involving the five basictastes

25 Relationship between LMSG Secretion and Nearby BFChange following Taste Stimulation TheLMSG secretion andnearby BF changes in the labial mucosa following applicationof the highest concentration (No 5) of each of the five basictaste solutions onto the posterior tongue were observed for14 participants The LMSG secretion was first measured andthen the BF change to the tastant was measured until the BFhad recovered to the prestimulus value

26 Use of Autonomic Agents The following four autonomicagents were prepared

(i) 01 adrenaline a sympathomimetic agent (Adren-aline Injection 01 Terumo Corporation TokyoJapan)

(ii) 3 cevimeline hydrochloride aqueous solution amuscarinic (M3) receptor agonist (Saligren capsule30mg Nippon Kayaku Tokyo Japan)

(iii) 1 atropine sulfate hydrate a cholinergic blockingagent (atropine ophthalmic solution 1 Nitten Phar-maceutical Co Ltd Nagoya Japan)

(iv) 25 pirenzepine hydrochloride aqueous solutiona muscarinic (M1) receptor antagonist (pirenzepinehydrochloride tablets 25mg Nichi-Iko Pharmaceuti-cal Co Ltd Toyoma Japan)

The concentration of each autonomic agent was basedon the manufacturerrsquos medical package insert for clinicaluse The LMSG flow rate and BF were measured followingapplication of a 3 times 1 cm filter paper soaked in 50 120583L ofeach agent or DW on the labial mucosa for 5min in 11participants Stimulation with the next agent was appliedafter the measurement values had returned to the baselinelevel The participants were asked to rinse their mouth withwater and an interval of at least 30min was set between eachstimulation

27 Data Analysis TheLMSG secretion after the administra-tion of DW tastants or autonomic agents is presented as apercentage of the resting value (mean plusmn standard deviation)To compare each mean to the control (DW) mean the datawere analyzed by one-way analysis of variance followed byDunnettrsquos multiple-comparison test Tukeyrsquos honestly signif-icant difference test was used to analyze the differences inLMSG secretion and BF changes following stimulation withvarious tastants

The BF changes in the labial mucosa after the administra-tion of DW tastants or autonomic agents are presented as apercentage of the baseline value recorded with no adminis-tration (mean plusmn standard deviation) To compare each mean

to the control (DW) mean the data were analyzed by one-way analysis of variance followed by Dunnettrsquos multiple-comparison test

The normality of the data was assessed using the Shapiro-Wilk test and the correlation between the changes inLMSG secretion and the nearby BF was then statisticallyanalyzed using Spearmanrsquos rank correlation All statisticalanalyses were performed using SPSS 180 (SPSS Inc ChicagoIL USA) The criterion for significance was defined as119901 lt 005

3 Results

31 Changes in LMSG Secretion following Stimulation withFive Basic Tastes Low concentrations of the five basic tastes(sweet salty sour bitter and umami) caused no signifi-cant changes in LMSG secretion however high concentra-tions (Nos 3ndash5) of all tastes evoked significant increasesin LMSG secretion (Figure 1) Table 1 shows the detailedresults

As shown in Table 2 sour and umami tastes evokedsignificantly larger increases in LMSG secretion than did theother tastes (sweet salty and bitter) at high concentrations(Nos 4 and 5) although low concentrations (Nos 1ndash3) theydid not

32 Changes in LMSG Secretion following Stimulation withMixed Umami Substances Mixed umami substances of5mM MSG and 5mM IMP caused a significant increase inLMSG secretion (119901 lt 00001) while each solution aloneelicited no significant change (MSG G2 1041 plusmn 62 119901 =0985 IMP 1066 plusmn 68 119901 = 0886) as compared with DWstimulation (1018 plusmn 45) (Figure 2)

33 Relationship between LMSG and Nearby Lip BF followingTaste Stimulation The highest concentration (No 5) of eachof the five basic tastes evoked a significant increase in LMSGsecretion (sweet S5 1313 plusmn 193 119901 = 0045 salty N5 1308 plusmn111 119901 = 0049 sour T5 2648 plusmn 764 119901 lt 00001 bitter Q51310 plusmn 363 119901 = 0048 umami 2668 plusmn 476 119901 lt 00001)compared with DW stimulation (967 plusmn 08) (Figure 3(a))All tastes except bitter evoked a significant increase in lip BF(sweet S5 1345 plusmn 95 119901 = 0013 salty N5 1289 plusmn 86 119901 =0047 sour T5 2385 plusmn 438 119901 lt 00001 umami G5 2244 plusmn564119901 lt 00001) comparedwithDWstimulation (990plusmn25)while bitter did not elicit a significant change in BF (1189 plusmn291 119901 = 0295) (Figure 3(b)) As shown in Tables 3 and 4sour and umami tastes evoked significantly larger increasesin both LMSG secretion and BF changes than did the othertastes (sweet salty and bitter) Some participants showedincreases in both LMSG secretion and BF change in responseto bitter taste but others showed decreases in both LMSGsecretion and BF change Comparison of the changes in thesame participants revealed a significant correlation betweenthe amount of changes in salivation and BF in response toeach taste stimulus (sweet 119903 = 0802 salty 119903 = 0751sour 119903 = 0806 bitter 119903 = 0805 umami taste 119903 = 0853)(Figure 4)


S2 S3 S4 S5DW S10

50

100

150

200

250

300Sa

liva s

ecre

ted

from

LM

SGs (

)

lowastlowast

lowastlowastlowastlowast

(a) Sweet stimulationN2

0

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100

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300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

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lowastlowast

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(b) Salty stimulation

T2 T3 T4 T5DW T10

50

100

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300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

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lowastlowast

(c) Sour stimulation

Q2 Q3 Q4 Q5DW Q10

50

100

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300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast

(d) Bitter stimulation

G2 G3 G4 G5DW G10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

()

lowastlowast

lowastlowast

lowastlowast

(e) Umami stimulation

Figure 1 Changes in LMSG secretion following stimulation with five basic tastes High concentrations (Nos 3ndash5) of each of the five basictastes (S N T Q and G) elicited a significant increase in LMSG secretion in human participants (119899 = 21) although lower concentrations(Nos 1 and 2) of each solution caused no significant change Ordinate a percentage () of the resting saliva lowast119901 lt 005 lowastlowast119901 lt 00001


Table 1 Changes in LMSG secretion induced by DW or tastants

DW 1 2 3 4 5S (sweet)

change 995 plusmn 23 991 plusmn 26 1004 plusmn 41 1128 plusmn 87 1255 plusmn 166 1264 plusmn 255

119901 values - 0999 0998 lt00001lowastlowast lt00001lowastlowast lt00001lowastlowast

N (salty) change 1006 plusmn 30 985 plusmn 22 1089 plusmn 87 1141 plusmn 125 1187 plusmn 141 1198 plusmn 166


T (sour) change 987 plusmn 28 993 plusmn 32 1111 plusmn 72 1342 plusmn 158 1742 plusmn 357 2724 plusmn 425

119901 values - 0999 0696 0007lowast lt00001lowastlowast lt00001lowastlowast

Q (bitter) change 1040 plusmn 19 977 plusmn 19 1051 plusmn 97 1151 plusmn 189 1190 plusmn 268 1211 plusmn 343


G (ummai) change 985 plusmn 29 996 plusmn 31 1094 plusmn 54 1225 plusmn 186 1637 plusmn 325 2686 plusmn 421


Statistical differences were analysed by one-way ANOVA and Dunnettrsquos multiple-comparison test (lowast119901 lt 005 lowastlowast119901 lt 0001) change indicates a percentageof the resting value (mean plusmn standard deviation) 119899 = 21

Table 2 Increases in LMSG secretion induced by high concentration of tastants (No 4 and 5)

S (sweet) N (salty) T (sour) Q (bitter) G (umami)

No 4

S (sweet) - 0977 lt0001lowast 0949 lt0001lowast

N (salty) - lt0001lowast 1000 lt0001lowast

T (sour) - lt0001lowast 021Q (bitter) - lt0001lowast

G (umami) -

No 5




G (umami) -Statistical differences were analysed by one-way ANOVA and Tukeyrsquos honestly significant difference test numerical value means 119901 value between one tastantand another lowast (asterisk) means significant 119899 = 21

34 Changes in LMSGSecretion andNearby Lip BFChange fol-lowing Stimulation with Autonomic Agents Administrationof cevimeline chloride (parasympathetic agonist) caused asignificant increase in LMSG secretion (1703 plusmn 221 119901 lt00001) while adrenaline (sympathetic agonist) (332 plusmn 38119901 lt 00001) atropine (parasympathetic inhibitor) (640plusmn61119901 lt 00001) and pirenzepine (parasympathetic antagonist)(423 plusmn 84 119901 lt 00001) evoked a significant decrease inLMSG secretion comparedwithDW stimulation (1034plusmn34)(Figure 5(a)) These changes induced by the different agentswere consistent with those of nearby lip BF changes that iscevimeline chloride caused a significant increase in the BF(1989 plusmn 371 119901 lt 00001) while adrenaline (377 plusmn 92 119901 lt00001) atropine (619 plusmn 122 119901 lt 00001) and pirenzepine(496 plusmn 188 119901 lt 00001) elicited a significant decreasein the BF compared with DW stimulation (1068 plusmn 72)(Figure 5(b)) Significant correlations were found betweenthe amount of change in LMSG secretion and the BF foreach autonomic agent in the same participant (adrenaline

119903 = 0893 cevimeline 119903 = 0882 atropine 119903 = 0797pirenzepine 119903 = 0788) (Figure 6)

4 Discussion

41 Responses ofMinor SalivaryGland Secretion to Stimulationwith Five Different Tastes The gustatory-salivary reflex (ietaste-initiated secretion of saliva) is important for tastingmasticating and swallowing food This vital reflex has beenmainly studied in the saliva secreted from the major salivaryglands or mixed saliva secreted from the major and minorsalivary glands Kerr [12] showed that the human majorsalivary flow response to citric acid salt and sucrose was10 7 and 4 times higher than the resting saliva responserespectively Hodson and Linden [13] also demonstrated thatthe five basic taste qualities (sweet salty sour bitter andumami) induced the gustatory-salivary reflex in the parotidgland and that parotid salivary flow increased in a dose-dependent manner in response to umami taste (MSG)


Table 3 Increases in LMSG secretion induced by tastant of No 5


No 5




G (ummai) -Statistical differences were analysed by one-way ANOVA and Tukeyrsquos honestly significant difference test numerical value means 119901 value between one tastantand another lowast (asterisk) means significant 119899 = 14

Table 4 Increases in BF change induced by tastant of No 5


No 5




G (ummai) -Statistical differences were analysed by one-way ANOVA and Tukeyrsquos honestly significant difference test numerical value means 119901 value between one tastantand another lowast (asterisk)means significant 119899 = 14

Saliva secreted from LMSGs

DW MSG (G2) IMP MSG + IMP0

50

100

150

200

250

()

lowast

Figure 2 Changes in LMSG secretion following stimulation withumami substances Neither MSG (G2) nor IMP elicited a significantchange in LMSG secretion while mixed umami substance (5mMMSG + 5mM IMP) caused a significant increase in LMSG secretion(119901 lt 00001) (119899 = 10) lowast119901 lt 00001 Ordinate a percentage () ofthe resting saliva

Few reports have provided a detailed comparison ofgustatory-salivary reflex salivation in response to the dif-ferent taste stimuli in the minor salivary glands exceptour preliminary report [14] because of the difficulty inmeasurement of the minute secretion volume from theminor salivary glands In the present study we used a newlydeveloped method for measuring the LMSG flow rate [7]and demonstrated that (1) each of the five basic taste stimulielicited a significant increase in saliva secreted from theLMSG in a dose-dependent manner and (2) sour and umamitastes elicited significantly larger increases in LMSG secretionthan did sweet salty or bitter These results are consistentwith previous reports demonstrating the major salivary flowresponse [13 15 16]

Allen [17] reported a correlation between gustatory-salivary reflex salivation in the parotid gland and the intensityof the taste stimulus Therefore the taste intensity of eachdifferent taste quality must be equivalent to compare thedifferences in the amount of saliva produced by the gustatory-salivary reflex In the present study each different tastequality solution including umami was administered at fivedifferent intensities (Nos 1ndash5) based on a previous studythat established the cumulative distribution of each tastant[10 11] For example the specific taste quality of the No 2concentration of each taste solution can be recognized by50 of participantsThus using the same number of taste testsolutions it becomes possible to supply an equal intensity oftaste perception in spite of the differences in taste quality

42 Responses of LMSG Secretion to Stimulation with MixedUmami Substance Mixed umami solution containing MSGand IMP caused a significant increase in LMSG secretionwhereas stimulation withMSG or IMP alone did not increaseLMSG secretion at these concentrations The synergism ofumami tastes between MSG and guanylate was first reportedby Kuninaka [18 19] and Yamaguchi and Ninomiya [9] indi-cated that the detection threshold of umami taste perceptionof MSG was markedly lower in the presence of IMP A recentelectrophysiological study involving mice demonstrated theoccurrence of marked enhancement of the glossopharyngealnerve responses toMSG by the addition of guanylate [20 21]This is in line with our result on the synergism of umamitastes when the posterior tongue is stimulated by a mixtureof MSG and another umami substance (eg IMP) It hasbeen suggested that the human taste receptor a T1R1 + T1R3heterodimer induces potentiation of the synergism betweenMSG and IMP A recent study suggested the existence ofseparate binding sites forMSG and IMPwithin the sameT1R1Venus flytrap domain which is important for umami tastesynergism [22 23] In T1R1-knockout mice the synergism



DW S5 N5 T5 Q5 G50

50

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350(

) lowast

lowastlowast

lowastlowast lowastlowast

(a)

0

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()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)

Figure 3 Changes in (a) LMSG secretion and (b) nearby BF change following stimulation with five basic tastes (a)The highest concentration(No 5) of each of the five basic tastes (S N T Q and G) evoked significant increases in MSG secretion (119899 = 14) (b) The same concentrationof each of the basic tastes except bitter elicited a significant increase but not a significant change in labial mucosal BF (119899 = 14) Ordinate apercentage () of (a) the resting saliva and (b) the baseline BF value lowast119901 lt 005 lowastlowast119901 lt 00001

between MSG and IMP is considerably reduced in theanterior tongue [24] Thus the umami taste has a quitedistinguished synergistic effect exhibited by no other tastequalityWe demonstrated that the synergistic effect of umaminot only showed sensory perception but also evoked thegustatory-salivary reflex in the LMSGsThis synergistic effecthas also been shown to be elicited not only between MSGand IMP but also between MSG and other nucleotides ofguanylate [18 19] Therefore further studies of the effect ofdifferent mixtures of MSG and other nucleotides on reflexsecretion in the LMSGs are needed

Umami has another specific characteristic that is itsresidual aftertaste which differs from other taste qualities[25] In a preliminary study we examined the time courseof the salivary flow of LMSG secretion in response to thefive basic tastes and found that the umami taste evoked along-lasting increase in LMSG whereas sour taste evokeda prominent increase in the LMSG flow that immediatelydiminished [14] It seems likely that these long-lasting effectson LMSG secretion incidental to the umami taste are due tothe residual aftertaste The synergism and residual aftertasteof the umami taste may be beneficial for patients with drymouth based on our previous finding that xerostomia is morestrongly related to the LMSG flow than the major salivarygland flow [8]

43 Relationship between LMSG Secretion and Nearby LipBF Change following Taste Stimulation The salivary glandsare supplied by a dense capillary network equivalent tothat of the heart thus vasodilatation of these capillariessurrounding the salivary glands might be necessary to ensurethat large volumes of saliva are produced by the secretorycells [26 27]We considered that the circulation surroundingthe LMSGs is closely related to the LMSG secretory system

Consequently we examined the nearby lip BF where theLMSG secretion measurement was performed using laserDoppler flowmetry Our measurement of the BF includedthe labial glandular BF because laser Doppler flowmetrycan measure the erythrocyte flux through an approximately1mm3 volume of the capillary bed without touching thetissues [28] This can be accomplished because the LMSGsdensely exit via the superficial oral mucosa which is verythin We demonstrated that stimulation with all tastes exceptbitter caused an increase in the nearby lip BF consistentwith the increase in the LMSG secretion In addition sourand umami tastes induced prominent increases in the BF inthe same manner as the LMSG secretion Taste stimulationevoked no BP changes indicating that vasodilation in thestimulated area was induced

Interestingly we observed a correlation between the rateof changes in the BF and the LMSG response to eachtaste stimulus in different participants (Figure 4) As shownin Figure 4 sweet salty sour and umami tastes evokedcorrelated increases in the BF and LMSG secretion (gt100in the figure) in all participants however bitter caused acorrelated decrease in the BF and LMSG secretion (lt100in the figure) in some participants Thus bitter only evokeda BF decrease in some participants A previous study showedthat the BF in the orofacial area is uniquely controlled by adouble autonomic system that is vasoconstriction mediatedvia sympathetic nerve fibers and vasodilation mediated viaparasympathetic efferent nerve fibers [29] Bitter taste canevoke both sympathetically induced reflexive vasoconstric-tion and parasympathetically mediated vasodilation whilethe other tastes prominently induce reflex vasodilation Inthis respect the hedonic dimension to the taste report-edly plays various roles in the many taste-mediated whole-body responses Interestingly an unpleasant bitter taste can


80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802

(a) Sweet stimulation

40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853


Figure 4 Relationship between LMSG secretion and BF response in lip following taste stimulation Significant correlations were presentbetween the amount of change in LMSG secretion and BF evoked by the highest concentration (No 5) of each taste stimulus (119899 = 14)Ordinate a percentage () of the baseline BF value Abscissa a percentage () of the resting LMSG saliva

reportedly induce sympathetically mediated physiologicalchanges in skin BF and skin temperature instantaneousheart rate and skin potential and skin resistance much morestrongly than other taste qualities (sweet salty and sour) [30]Additionally pleasant stimuli were found to elicit approachand acceptance whereas unpleasant stimuli induced avoid-ance and rejection thus determining taste preferences and

aversions [30] Although we did not record the participantsrsquoliking of each tastant in this experiment some participantsindeed hated the bitter taste Such individuals may showstronger decreases in LMSG secretion and the BF as asympathetic effect Further studies are needed to clarify therole of unpleasant taste sensations in the control of taste-mediated responses related to food rejection



lowast

lowast

lowast

lowast

0

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()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

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()

Pire

nzep

ine

Atro

pine

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imel

ine

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nalin

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DW

Labial BF change

(b)

Figure 5 Changes in (a) LMSG secretion and (b) nearby BF change following stimulation with autonomic agents onto the lip (a)Administration of cevimeline chloride caused a significant increase in LMSG secretion (119901 lt 0001) while adrenaline atropine andpirenzepine evoked significant decreases in LMSG secretion (119899 = 11) (b) Cevimeline chloride caused a significant increase in labial mucosalBF while adrenaline atropine and pirenzepine elicited significant decreases (119899 = 11) Ordinate a percentage () of the (a) resting saliva and(b) baseline BF lowast119901 lt 00001

Overall our results indicate that the BF change surround-ing the LMSGs is an important factor in the salivary secretorysystem in the LMSGs

44 LMSG Secretion and Nearby Lip BF Changes Mediatedby the Autonomic Nervous System Salivary secretion iscontrolled by the parasympathetic and sympathetic auto-nomic nervous systems [31] In the human parotid glandthe gustatory-salivary reflex involves the activity of bothtypes of autonomic nerves while the masticatory-salivaryreflex preferentially activates the parasympathetic nerves[32] Mobilization of the intracellular messenger calcium bystimulation of muscarinic receptors (M1 M3) is associatedwith fluid secretion particularly large volumes in responseto muscarinic agonists via exocytosis in the rat parotid gland[33] However the neural regulation of the gustatory-salivaryreflex in human LMSGs remains unknown In the presentstudy application of cevimeline hydrochloride hydrate (anagonist of the muscarinic M3 receptor) onto the lip elicitedan increase in LMSG secretion Furthermore pirenzepine(an antagonist of the muscarinic M1 receptor) and atropine(a competitive inhibitor of the muscarinic acetylcholinereceptor) elicited a decrease in LMSG secretion Thus weconclude that muscarinic receptors (M1 M3) are engagedin human LMSG secretion However the application ofadrenaline (an agonist of 120572 and 120573 adrenergic receptors)certainly decreased LMSG secretion This phenomenon dif-fers from that described in a report on sympathetic nerve-induced secretion by the parotid gland suggesting that thehuman LMSGs may lack sympathetic secretion This idea

is supported by a histochemical study indicating that fewadrenergic nerves have been identified in the human LMSGs[34]

Nervous control of the orofacial BF is regulated by boththe parasympathetic and sympathetic autonomic nervoussystems [29] In the cat labial BF is controlled by twogroups of parasympathetic fibers (the facial and glossopha-ryngeal nerves) for vasodilatation [29] and by sympathetic 120572-adrenergic fibers for vasoconstriction [35]We also examinedthe neural regulation of the BF in the human labial mucosabecause salivary secretion appears to be related to the nearbyBF as mentioned above In our pharmacological analysisapplication of cevimeline hydrochloride hydrate (an agonistof the muscarinic M3 receptor) elicited a prominent increasein the BF without a change in the BP and pirenzepine (anantagonist of the muscarinic M1 receptor) and atropine (acompetitive inhibitor of the muscarinic acetylcholine recep-tor) elicited a significant decrease in the BF without a changein the BP indicating that muscarinic receptors (M1 M3)are engaged in vasodilatation in the human labial mucosaltissues surrounding the LMSGs Furthermore adrenaline(an agonist of 120572 and 120573 adrenergic receptors) elicited asignificant decrease in the nearby BF without a change inthe BP indicating that 120572-adrenergic receptors are involvedin vasoconstriction in this region Interestingly correlationswere found between the dynamics of the saliva secretedfrom the LMSGs and the nearby lip BF changes in responseto each chemical agent in the same participants (Figure 6)although vascular responses monitored by laser Dopplerflowmetry should include not only the labial glandular BF


0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine

Figure 6 Relationship between LMSG secretion and BF response in lip following stimulation with autonomic agent Significant correlationswere present between the amounts of change in LMSG secretion and BF evoked by each autonomic agent in the same participant (119899 = 11)Ordinate a percentage () of the baseline BF value abscissa a percentage () of the resting LMSG saliva

but also the mucosal capillary BF These results show thatparasympathetic activation can simultaneously increase thesalivary secretion from the LMSGs and induce vasodilatationin the mucosal tissues surrounding the LMSGs Converselydecreases in the saliva secreted by the LMSGs may be causedby a decrease in BF incidental to the vasoconstriction becausethe human LMSGs possibly lack sympathetic secretion asdiscussed above [34]Thus we consider that LMSG secretionis strongly influenced by the nearby BF Further detailedstudies are necessary to clarify the effects of the relationshipbetween LMSG secretion and nearby BF changes on theautonomic nervous system

The present study has shown that each of the five basictaste sensations can induce human LMSG secretion ThisLMSG secretion is an autonomic nervous system-inducedreflex that spontaneously arises at meals and may be benefi-cial to various functions of eating such as smooth chewing

and formation of a food bolus Moreover LMSG secretionprovides lubrication and protection of the oral mucosabecause the LMSG secretions contain high concentrations ofprotective substances such as mucin and immunoglobulin AThis LMSG secretion induced by taste substances containedin food atmeals would thus be beneficial formaintaining oralhealth

5 Conclusions

Taste stimulation can cause a gustatory-reflex secretion inthe human LMSGs In particular sour and umami tastescause larger increases in LMSG secretion than do other tastesUmami has a synergistic effect on the LMSG secretion reflexParasympathetic regulation is involved in the gustatory-salivary reflex in the LMSGs in association with the changesin BF near the LMSGs


Conflicts of Interest

All authors declare no conflicts of interest regarding thepublication of this paper

Acknowledgments

The authors greatly appreciate the participation of all indi-viduals in this study This study was supported in part byGrants-in-Aid for Developmental Scientific Research fromthe Ministry of Education Science and Culture of Japan(nos 22590575 and 24590780 to S Satoh-Kuriwada) andwas funded in part by the Ajinomoto Company (KanagawaJapan) Finally the authors thank Angela Morben DVMELS fromEdanzGroup for editing a draft of thismanuscript

References

[1] S A Rayment B Liu G D Offner F G Oppenheim and R FTroxler ldquoImmunoquantification of human salivary mucinsMG1 and MG2 in stimulated whole saliva Factors influencingmucin levelsrdquo Journal of Dental Research vol 79 no 10 pp1765ndash1772 2000

[2] JMCrawfordMA Taubman andD J Smith ldquoMinor salivaryglands as a major source of secretory immunoglobulin A in thehuman oral cavityrdquo Science vol 190 no 4220 pp 1206ndash12091975

[3] C Dawes and C M Wood ldquoThe contribution of oral minormucous gland secretions to the volume of whole saliva in manrdquoArchives of Oral Biolog vol 18 no 3 pp 337ndash342 1973

[4] A C Dale ldquoSalivary glandsrdquo in Oral histology developmentstructure and function C Ten Ed pp 303ndash331 Mosby Com-pany St Louis MO USA 1985

[5] M P Hector and R W A Linden ldquoReflexes of salivarysecretionrdquo in Neural mechanisms of salivary glands Frontiers ofOral Biology R Garrett J Ekstrom and L C Andersson Edsvol 11 Kargel Basel Switzerland 1999

[6] J Ekstrom N Khosravani M Castagnola and I MessanaldquoSaliva and the Control of Its Secretionrdquo in Dysphagia MedicalRadiology pp 19ndash47 Springer Berlin Heidelberg Berlin Hei-delberg 2012

[7] N Shoji T Sasano K Inukai et al ldquoA simple yet accu-rate method for detecting and quantifying secretions fromhuman minor salivary glands using the iodine-starch reactionrdquoArchives of Oral Biolog vol 48 no 11 pp 761ndash765 2003

[8] S Satoh-Kuriwada M Iikubo N Shoji M Sakamoto and TSasano ldquoDiagnostic performance of labial minor salivary glandflow measurement for assessment of xerostomiardquo Archives ofOral Biolog vol 57 no 8 pp 1121ndash1126 2012

[9] S Yamaguchi and K Ninomiya ldquoUmami and food palatabilityrdquoThe Journal of Nutrition vol 130 pp 921Sndash926S 2000

[10] S Satoh-KuriwadaM KawaiM Iikubo et al ldquoDevelopment ofan Umami taste sensitivity test and its clinical userdquo PLoS ONEvol 9 no 4 Article ID e95177 2014

[11] H Tomita M Ikeda and Y Okuda ldquoBasis and Practice ofClinical Taste Examinationsrdquo Auris Nasus Larynx vol 13 ppS1ndashS15 1986

[12] A C Kerr A study of the response of human salivary glandsto reflex stimulation The Physiological Regulation of SalivarySecretion in Man Pergamon Press New York NY USA 1961

[13] N A Hodson and RW A Linden ldquoThe effect of monosodiumglutamate on parotid salivary flow in comparison to theresponse to representatives of the other four basic tastesrdquoPhysiology amp Behavior vol 89 no 5 pp 711ndash717 2006

[14] T Sasano S Satoh-Kuriwada N Shoji et al ldquoImportant roleof umami taste sensitivity in oral and overall healthrdquo CurrentPharmaceutical Design vol 20 no 16 pp 2750ndash2754 2014

[15] H H Chauncey and I L Shannon ldquoParotid Gland SecretionRate as Method for Measuring Response to Gustatory Stimuliin Humansrdquo Proceedings of the Society for Experimental Biologyand Medicine vol 103 no 3 pp 459ndash463 1960

[16] R L Speirs ldquoThe effects of interactions between gustatorystimulation the reflex flow-rate of human parotid salivardquoArchives of Oral Biolog vol 16 no 4 pp 349ndash365 1971

[17] F Allen ldquoThe secretory activity of the parotid glandrdquo Experi-mental Physiology vol 19 no 4 pp 337ndash362 1929

[18] A Kuninaka ldquoStudies on Taste of Ribonucleic Acid Deriva-tivesrdquo Nippon Nogeikagaku Kaishi vol 34 no 6 pp 489ndash4921960

[19] A Kuninaka ldquoThe nucleotides a rationale of research onflavor potentiationrdquo in Proceedings of the Symposium on FlavorPotentiation p 4 Cambridge MA 1964

[20] Y Ninomiya T Tanimukai S Yoshida and M FunakoshildquoGustatory neural responses in preweanling micerdquo Physiologyamp Behavior vol 49 no 5 pp 913ndash918 1991

[21] Y Nimomiya and M Funakoshi ldquoPeripheral neural basis forbehavioural discrimination between glutamate and the fourbasic taste substances in micerdquo Comparative Biochemistry andPhysiology - Part A Molecular amp Integrative Physiology vol 92pp 371ndash376 1989

[22] F Zhang B Klebansky RM Fine et al ldquoMolecularmechanismfor the umami taste synergismrdquo Proceedings of the NationalAcadamy of Sciences of the United States of America vol 105no 52 pp 20930ndash20934 2008

[23] S Damak M Rong K Yasumatsu et al ldquoDetection of sweetand umami taste in the absence of taste receptor T1r3rdquo Sciencevol 301 no 5634 pp 850ndash853 2003

[24] Y Kusuhara R Yoshida T Ohkuri et al ldquoTaste responses inmice lacking taste receptor subunit T1R1rdquo The Journal ofPhysiology vol 591 no 7 pp 1967ndash1985 2013

[25] T Horio and Y Kawamura ldquoStudies on after-taste of varioustaste stimuli in humansrdquo Chemical Senses vol 15 no 3 pp 271ndash280 1990

[26] A V Edwards ldquoAutonomic control of salivary blood flowrdquo inGlandular mechanisms of salivary secretion Frontiers of OralBiology R Garrett J Ekstom and L C Anderson Eds vol10 Karger Basel Switzerland 1998

[27] L H Smaje ldquoCapillary dynamics in salivary glandsrdquo in Glan-dular mechanisms of salivary secretion Frontiers of Oral BiologyR Garrett J Ekstom and L C Anderson Eds vol 10 KargerBasel Switzerland 1998

[28] T Sasano N Shoji S Kuriwada and D Sanjo ldquoCalibrationof laser Doppler flowmetry for measurement of gingival bloodflowrdquo Journal of Periodontal Research vol 30 no 4 pp 298ndash301 1995

[29] H Izumi and K Karita ldquoVasodilator responses followingintracranial stimulation of the trigeminal facial and glossopha-ryngeal nerves in the cat gingivardquo Brain Research vol 560 no1-2 pp 71ndash75 1991

[30] S Rousmans O Robin A Dittmar and E Vernet-MauryldquoAutonomic nervous system responses associated with primarytastesrdquo Chemical Senses vol 25 no 6 pp 709ndash718 2000


[31] J R Garrett ldquoHistorical introduction to salivary secretionrdquo inGlandular Mechanisms of Salivary Secretion J R Garrett JEkstrom and L C Anderson Eds vol 10 Karger BaselSwitzerland 1998

[32] J C J Kjeilen P Brodin H Aars and T Berg ldquoParotid salivaryflow in response to mechanical and-gustatory stimulation inmanrdquo Acta Physiologica Scandinavica vol 131 no 2 pp 169ndash175 1987

[33] J Ekstrom ldquoMuscarinic agonist-induced non-granular andgranular secretion of amylase in the parotid gland of theanaesthetized ratrdquo Experimental Physiology vol 87 no 2 pp147ndash152 2002

[34] R B Rossoni A B Machado and C R S Machado ldquoAhistochemical study of catecholamines and cholinesterases inthe autonomic nerves of the humanminor salivary glandsrdquoTheHistochemical Journal vol 11 no 6 pp 661ndash668 1979

[35] H Izumi S Kuriwada K Karita T Sasano and D Sanjo ldquoThenervous control of gingival blood flow in catsrdquo MicrovascularResearch vol 39 no 1 pp 94ndash104 1990

Hindawiwwwhindawicom

International Journal of

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Zoology

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Anatomy Research International

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The Scientific World Journal

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MicrobiologyHindawiwwwhindawicom

Nucleic AcidsJournal of

Volume 2018

Submit your manuscripts atwwwhindawicom


2 Materials and Methods

21 Participants and Exclusion Criteria In total 64 healthyparticipants were initially recruited from the students atTohoku University and the residents and staff membersat Tohoku University Hospital Individuals with systemicdisease (eg endocrine infectious or immunological diseaseor a history of chemotherapy andor radiation therapy forhead and neck cancer) who had been prescribed medi-cations that could directly affect dry mouth or who hada feeling of oral dryness were excluded Individuals withhyposalivation identified by measuring the LMSG flow andthose with a history of psychological problems were alsoexcluded after careful interviews and psychological testing(Self-Rating Depression Scale) to avoid psychogenic oraldryness Consequently 56 individuals (average age 312plusmn83years age range 19ndash42 years 44 men 12 women) were finallyincludedThese participants were divided into four groups toevaluate the LMSG responses to taste (119899 = 21) the synergisticeffect of umami (119899 = 10) the relationship between LMSGsecretion and the BF change where the LMSG are located(119899 = 14) and the involvement of the autonomic nervoussystem in LMSG secretion and the BF change (119899 = 11) Thisstudy was designed and conducted in complete accordancewith the World Medical Association Declaration of Helsinki(httpwwwwmanet) and was approved by the Ethics Com-mittee of the Tohoku University Graduate School of Den-tistry Written consent was obtained from each participantafter they had received an explanation of the purpose of thestudy

22 Quantification of LMSG Secretion The LMSG secretionresponses to distilled water (DW) tastants or autonomicagents were quantified using the iodine-starch filter papermethod as previously described [7] Briefly a strip of testpaper (3 times 1 cm Filter paper 1 Toyo Roshi Kaisha LtdTokyo Japan) painted with a solution of iodine in absolutealcohol and a fine starch powder mixed with castor oil wasapplied onto the lower lip for 2min [7]Theblackened areas ofeach test paper imprinted by the iodine-starch reaction werescanned and digitized at 8 bits using a GT-9500 ART imagescanner (Seiko Epson Corp Nagoya Japan) with the scan-ning resolution set at 144 dpi The total area was measuredusing image analysis software (Scion Image Beta 402 ScionCorporation Frederick MD USA) Each total area value wasconverted to a flow rate (120583Lcm2min) using the calibrationline119884 = minus0084+24992119883 (119884 area inmm2119883 volume in 120583L)previously described [7]

23 BF Measurements in Labial Mucosa BF changes in thelower labial mucosa where quantification of the LMSGsecretion was undertaken were continuously monitoredusing reflection-mode laser Doppler flowmetry (SNF12007Cyber Firm Med Inc Tokyo Japan) before and after theadministration of DW tastants or autonomic agents Duringmeasurement of the BF the participants were asked to keeptheir mouths open and the lower lip was everted using anangle widener The test areas were isolated with rolled gauzeand then dried with a cotton gauze pad immediately before

the recording was performed A sensor probe was firmlyanchored to the angle widener with surgical tape and thetip of the probe was kept at a distance of 05mm from thelip surface All recordings were electrically calibrated to zeroBF Laser Doppler signals from the lower labial mucosa werecontinuously monitored together with the systemic bloodpressure (BP) (Finometer Finapres Medical Systems Ams-terdam Netherlands) The outputs from the flowmeter andBP monitor were recorded on a multichannel chart recorder(Recti-Horiz-8K NEC San-ei Tokyo Japan)

24 Taste Stimulation

241 Five Basic Tastes Five well-established taste substanceswere used For the four basic tastes (sweet salty sour andbitter) ready-made test solutions of Taste Disc (SanwaChemical Co Ltd Nagoya Japan) were used Each concen-tration of the four basic tastes was as follows

(i) Sweet (sucrose) 87mM (No 1 S1) 730mM (No 2S2) 2921mM (No 3 S3) 5842mM (No 4 S4) and23371mM (No 5 S5)

(ii) Salty (NaCl) 513mM (No 1 N1) 2138mM (No 2N2) 8555mM(No 3N3) 17111mM(No 4N4) and34223mM (No 5 N5)

(iii) Sour (tartaric acid) 13mM (No 1 T1) 133mM (No2 T2) 1332mM (No 3 T3) 2665mM (No 4 T4)and 5330mM (No 5 T5)

(iv) Bitter (quinine) 003mM (No 1 Q1) 05mM (No 2Q2) 25mM (No 3 Q3) 126mM (No 4 Q4) and1007mM (No 5 Q5)

For umami tasteMSGaqueous solution previously devel-oped for an umami taste sensitivity test [10] was used Theconcentrations of the umami taste were 1mM (No 1 G1)5mM (No 2 G2) 10mM (No 3 G3) 50mM (No 4 G4) and100mM (No 5 G5) Each taste number (Nos 1ndash5) was set upso that the intensity of the participantrsquos perception of the tastewas equivalent in spite of the different taste qualities basedon previously reported data of the Taste Disc [11] and ourpreviously described findings regarding umami [10] Thusthe intensity of perception of the same taste number (Nos1ndash5) was equal among the five tastes

A 5mm diameter cotton ball containing 50 120583L of eachtaste solution or DW was applied onto the posterior tonguefor 2min and the LMSG secretion was then measured Theparticipants were asked to rinse their mouth with water forat least 15min between each taste stimulation The next tastestimulation was applied after the measurement value hadreturned to the baseline level All participants (119899 = 21)were asked to refrain from eating or drinking (except water)smoking and brushing their teeth for at least 3 h beforetesting

242 Combined Umami Tastes of MSG and IMP To inves-tigate the well-known synergistic effect of combined umamitastes on LMSG secretion 5mM of MSG aqueous solution5mM of IMP aqueous solution and a solution containinga mixture of the two (5mM MSG and 5mM IMP) were














3 Results






S2 S3 S4 S5DW S10

50

100

150

200

250

300Sa

liva s

ecre

ted

from

LM

SGs (

)

lowastlowast



0

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

N3 N4 N5DW N1

lowastlowast

lowastlowast

lowastlowast


T2 T3 T4 T5DW T10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


Q2 Q3 Q4 Q5DW Q10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


G2 G3 G4 G5DW G10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

()

lowastlowast

lowastlowast

lowastlowast





DW 1 2 3 4 5S (sweet)














No 4




G (umami) -

No 5







4 Discussion





No 5







No 5







50

100

150

200

250

()

lowast







DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018















3 Results






S2 S3 S4 S5DW S10

50

100

150

200

250

300Sa

liva s

ecre

ted

from

LM

SGs (

)

lowastlowast



0

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

N3 N4 N5DW N1

lowastlowast

lowastlowast

lowastlowast


T2 T3 T4 T5DW T10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


Q2 Q3 Q4 Q5DW Q10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


G2 G3 G4 G5DW G10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

()

lowastlowast

lowastlowast

lowastlowast





DW 1 2 3 4 5S (sweet)














No 4




G (umami) -

No 5







4 Discussion





No 5







No 5







50

100

150

200

250

()

lowast







DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018



S2 S3 S4 S5DW S10

50

100

150

200

250

300Sa

liva s

ecre

ted

from

LM

SGs (

)

lowastlowast



0

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

N3 N4 N5DW N1

lowastlowast

lowastlowast

lowastlowast


T2 T3 T4 T5DW T10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


Q2 Q3 Q4 Q5DW Q10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

s (

)

lowast

lowastlowast

lowastlowast


G2 G3 G4 G5DW G10

50

100

150

200

250

300

Saliv

a sec

rete

d fro

m L

MSG

()

lowastlowast

lowastlowast

lowastlowast





DW 1 2 3 4 5S (sweet)














No 4




G (umami) -

No 5







4 Discussion





No 5







No 5







50

100

150

200

250

()

lowast







DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018




DW 1 2 3 4 5S (sweet)














No 4




G (umami) -

No 5







4 Discussion





No 5







No 5







50

100

150

200

250

()

lowast







DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018





No 5







No 5







50

100

150

200

250

()

lowast







DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018




DW S5 N5 T5 Q5 G50

50

100

150

200

250

300

350(

) lowast

lowastlowast


(a)

0

50

100

150

200

250

300

()

DW S5 N5 T5 Q5 G5


lowastlowast

Labial BF change

(b)








80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018



80 120 16040LMSG ()

40

80

120

160

BF (

)

r = 0802


40

80

120

160

BF (

)

80 120 16040LMSG ()

r = 0751


100 200 300 4000LMSG ()

0

100

200

300

BF (

)

r = 0806


40 80 120 1600LMSG ()

0

40

80

120

160

BF (

)

r = 0805


0

100

200

300

BF (

)

100 200 300 4000LMSG ()

r = 0853







lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018




lowast

lowast

lowast

lowast

0

50

100

150

200

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

(a)

lowast

lowast

lowastlowast

0

50

100

150

200

250

()

Pire

nzep

ine

Atro

pine

Cev

imel

ine

Adre

nalin

e

DW

Labial BF change

(b)







0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018



0

20

40

60BF

()

10 20 30 400LMSG ()

r = 0893

(a) Adrenaline

0

100

200

300

BF (

)

50 100 150 200 2500LMSG ()

r = 0882

(b) Cevimeline

20 40 60 800LMSG ()

0

20

40

60

80

100

BF (

)

r = 0797

(c) Atropine

0

20

40

60

80

BF (

)

20 40 600LMSG ()

r = 0788

(d) Pirenzepine





5 Conclusions





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018





Acknowledgments


References







































Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018










Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018




Volume 2018

Zoology











Volume 2018

















Advances in




Enzyme Research





Volume 2018


Documents

Effects and Mechanisms of Tastants on the Gustatory ...downloads.hindawi.com/journals/bmri/2018/3847075.pdf · ResearchArticle Effects and Mechanisms of Tastants on the Gustatory-Salivary