XIV

TRANSMISSION OF EXCITATION IN VISUAL CORTICAL SLICES VISUALIZED BY OPTICAL RECORDING MANBU..TAN_I_FUJI_,. .RJ.PJ_TA_RQ..SUNABA ATSUSHI YAMANAKA, .AN.D KEISUI(E. 'I'Q.YA@A, I ._ _ ._ . . Nat1 _ _ _.._.... *. . Lnst 2 ..P~~sio~.~..Sci....,.. .bfx~dai.ii, .~kz.aki ?.A& ..Ja~m

In the visual cortex (VC) excitation has been long been supposed to propagated along the columnar structures, but it has never been visualized. The present study aimed to visualize the propagation of neural excitation in VC by using the optical recording technique. The transverse slices dissected from a rat VC were stained with a voltage sensitive dye (RH482), and optical responses (OR) corresponding to the neural events in the VC were evoked by white matter (WM) stimulation. The time course of the ORs were recorded by a photodiode array, and time-lapse images of the ORs were taken by a cooled CCD video camera with strobe illumination at different time-lags after the stimulation. The results revealed columnar propagation (width 500 urn) of excitation along the neuronal chain of VC (WM -> layer 4 ->layer2-3). Further the evidence for the role of lateral inhibition in the control of spatial spread of columnar propagation was provided by two experiments. 1) Blockade of the GABA mediated inhibition with bicuculline did not significantly affected the initial process of the columnar propagation, but the excitation in layers 2-3 and 5-6 continued to extend in horizontal direction and spread over the entire VC slice. 2) In paired stimulation by two separate electrodes placed in WM (distance, 1 mm), remarkable shrinkage of the excitation column produced by one stimulus when it is preceded by another stimulus.

ORGANOTYPICSLICECULTURESOFNEURALTISSUE

B.H.GWHWILER. Brain Research Institute, Universitv of Zilrich. Aupust Forel-Strasse 1. CH8029 Zurich, Switzerland

The basic principle of the slice culture technique consists of attaching slices of any brain region onto glass coverslips,

and incubating them in rotating g tissue culture tubes for several weeks. The slow rotation results in a periodic alteration of

the gas/liquid interface to which the cultures are exposed. This process not only facilitates gas and medium exchange, but also leads to considerable thinning, thus allowing identified cells to be observed in living unstained tissue.

There are several advantages of this technique which are unique, at least in this combination: First, organotypic slice

cultures retain important features of the characteristic cellular and histological organization of the tissue of origin. Second,

the monolayer organization facilitates morphological observation as well the use of advanced electrophysiological and

optical recording techniques. Third, nerve cells in slice cultures display a high degree of cellular differentiation and therefore make it possible to morphologically identify cell types. Fourth, slice cultures permit studies of the development of

axonal connectivities within and between different brain areas by making use of the co-culture approach.

NITRIC OXILl& : A N 0 V E 1. N E 11 K II N A 1. M t', S S E N I; E Ii SULflMON.H.SNYDEK,Thc Johns ttopklns Ilnivcrsity School of Med~~:~rie Department. oi Neuroscicnce725 North Wolfe St,rcet,Baltrmor(t, Maryland 212Ufi U.S.A.

UOING NtilJKOtilULUGY IN FKUC UUCYTES RICARII HILEDl,l)epartment of Psychobiology,Laboratory ot' ICelIutar and Holec~~lar Ne~rrobiolosy,Unrvcrsity of Calrlornra lrvrne,C:\ !127ti. II. S. A.

SLOW ACTIONS OF FAST TRANSHITTEKS 1N THE ttIt't'OCAMt'lJS B.H.tiAHWJLEK, Brain Kesearch lrrstitute,Ar~gr~st-~orci Strassc 1, CH-8U29 Zurich, Switzerland