Appfiquge, C.N.R.& 9,gi90

(Recei:ved t 8 ~ ; Igl~:iiRevised version received April g~h, 1982; Ace-~ted April 20th, 1982}

Key word~: hipwocamlya~ - fieM potentials i~ vDo - GABA - aeetyleholir.¢

I~ ra~s under ure~hane anesthesia, a twin set of rnulfibar~eled m, icropipf, ttes was t~aed to record sirs u,s|y N si~U the a~mattc po~lat ian spike, gl~e positive field and lhe dendritic negative field

~eked by ¢ommi~sural s.~imulatian, and ~o apply microiomopt~ore~ieN~y GABA,ergic and d ~ i e e ~ a .g~s at each N~'N° Re~yi.ng on the Wpieat somatic responses evoked by local apNicat~on of GABA,a~,a ;¢~}KR0i~,e {ACh} , ' ~ e~e*rode can be positioned in ~he pyramidal la)'e, with good accuracy {iri ~te ra!g~ of 50 am) ~ d ~he p|f~rmacology of the eacit.atory drive impingi~g t~i~o~t ~he apical dendrite eon~m~tafi~.ly investigated.

~Cw~ CkA} AS f i rst de~¢riDed 20 years ago, p rom~m~t f e c m ~ : L ~PoPs arc ~,~d~,y '~ ........ ~"

from p~amida~ co ts in fi~e h i p p ~ a v a p a } fo ra~a t io l ~S]. ~{owcvcr, m spite o f these

pa r t i cu l a r l y powerfl.fi ~nhibitory potent ia ls - ' ~ ~°" " ' +~ " " '> . . . . . . . . . . . . .

~pfleptogen~:s~s,

" the excka to ry

• ¢ reoen£ studies

occvtpies a ¢en~

: and ing of" these

mcora i ta~ t l y ia

~n the d e n d r i t k

apply va r ious

© m V

,

, ~ h ~ 0 0 nA

t . . . . . . . . . . . J g A l A 5 0 h A t . . . . . . . . . . ~ G A l A ~ O ~ A

®

® MUSC~MOL

SR ~

2 ~ V

2,̧ ţ

acetate and the remaining barrels t M at pH 4),, and various agonists ~a1[y appiied at regnfar ~n~.erva~ ~e e~eetrode~ was routi~e~y checked

~g the deposit of Po~tam~ne sky blue

aM The profile o f the field responae~ ;Ml~ be described briefly since it aas beer~,

e×ter~iwI~7 ~r~ve.~figated previously (see rev}ew iaref , 1}, W}th a twin ,~et of ~}cordi~g electrode, a {i~t~ ~ip distaace 2.2,0-,250 ~,~m, a~im.~a~;ioa a 3--10 V, ().~-~.0o2 ~aec0 Hz} ~ e seq~ae}~c¢ of ever~tg is as follows: a negative field is firfl recorded 1 8 ~ #m from ~h,:~ ~urface, tN~ corresponds ~o the f~e~d EPSF ges~e~'ated }n aratum or~enso Approximately 2 ~ m frer~ the sarfw:,e, the dee~r e~ectrode record:, ~he typicai

m the

$ I k

I i I i I :'i "I, I . . . . . . . ]

{

~ C . ; % |

©

t

l O 0 ~ b

\

i 0 . . . . . . . o 0

A ~ ~ ~ t ~ ¸ r ~ t b ~

8

sh~

2~

a ~ { c ~ : ~ - h i ~ w e ~ e r , r~ot ~-~frefNently ,.,see. ~,~go !E) , the e n h a n c e m e n t was ~;~" ~

n g the appl ieaf ien~ one~ g h e i a h i b R e r y act ion had compie t e ty ~aded. Th is late r e s p o ~ : ; , w N c h has:r~o~ been o b ~ r v e d in ~it~'e [2], is no t due to .~ nonosp,~.afle

tished

' ,rats,

~onse loom ~ayer

o late

(Fig. ID), i n ,. a~ p rev ious ly no ted f~ the sJiee p r e p a r a t i o n [2], a p p l i c a t i o n o f G A B A (or muse~mol} i n s t ~ a m m rad~a~um (Fig. iF ) redfaced @~e f~e!d E P S P {a 50% r e d u c t i o n u~aally r equ i red less thar:~ 40 h A L T h e effect had a swift

oe_~et a n d offse t* s a d s h o w e d ~o, fadir~g or lNe respoese . The p r e s e m study therefoge ~hows that the late respor.~se and fad ing o f the fields are exd~).sive~y

' ~" - t : .-r m ~ l ~a or. ] ~:~s observaW~a ~s e ~ t l c w a r b r e l e v a ~ w~tb N~irI~:,N t g _ - ~ . ~ ¢ . P Y . a ~ . , ::Y, . .... . . . : - : . ~ o~- :..- ~ _o-- ° Y ~. : : . . . . ~.~,~m-r~ fr~ the m | e ~, .v~.d By the ~ah~b~v r~f GABAm,.me mb~b~tmn la %e cm,,et o f

: 2B) d o ~ e s . v m i e d betwe;er~ ~ : a ~ d m o r e ~g ~o t he • l~a f ion o f the p ipe t t e w~th r e g a r d t o tbe

~ ¢ , p y r a m ~ layer, l ike [he la~e r e s ~ s e [ndt~¢ed

¢~0 w h i c h ha s b e e n d bo~h h~ v ivo [4, 6] , a i¢ actieg~ ~.)f A C h on GAJBA release

{a = !6 rats) we have also coe~qrm.ed the p rev ious

.~. G g~ ~ a ......... ~ . . . . . ~ ¢ r ,~L~ ~ .......... o~ ..e~g° ~F), The ~ . ~ - ~ ~ • ~ - # ~ 4 ~ ' ,~ ~ •

a p p ~ t i e r ~ upe~ ~ ~ 1 ~ i, es+ ~ ~ + + m ~ Ng+ 2C~ ~ef ACi~ ( a ~ m u ~ p ~ ~m ~ meodni¢ , ~ e ref+ N N ~m u m N a depression e f the fi~ld EPSP (e $ ~ r e l ~ ' N ~ ~a~ ~ i ~

The o f conco~ i tm~t

(a) Wi,h a lore negatiee fietds are reex~d~ r re.the ; : appiicat+ior~ of ACh e o m i s ~ l y ~ r e d u e e the vi~:y: : dendritic EI~P. This thm the dendritic gems are ~ m a significant exNnt by ~matic l>otee+~Lals. (b) With Ngher imensi~y of stimulation O - N V. n = 8 raes), i the frequency of stimulation (2-3 Hz) readity produces a n of the ~pu~ation spike (Fig. 2++4 and ref. 9). Wid~ the double s ~ e m , this enhancement was often no~ed without dgnificm . . . . . . recorded concomitantly in the stratum radiatum discharge obtained daring e satanic a~p|iea:ioe of i induced by somatic applications o f GAB& e~ m~+cimoi (Ng+ iC+E) applications of GABA b~oeker~ (such as bicucuiiine+ aapuNished e ), are accompanied by lhtle or no alterations of t h e field E ~ P . i n kC~in~L wilh imraee~lular observatioe.~ [3, 5] thin Nrther ~ tres~ the imporiartce o f the |ability o f somatic ~nhibi~ion in promoting ~e~zure discharge.

| Anderses~° P++ Organization of hippoeampai neuron+ a~d the+i+: intefeonn~tion. [r~ R.L. ] ~ a c ~ and K.H, Prib~am ~Eds.L +CoL I. Fienum P~e+~. New York, ~975, pp. I~5+175.

2 Ande++ea, P.+ responses of hi~ (Lend.) 305 (1980) 279~296.

3 Ben+.kri, Y., Krnjevld, K° and Reinhardt, W., H J p ~ m ~ i ~zures at~d faiJure of inhibit.tar,+ Canad; 1+ Physiol. PharmacoL, 57:(1979) t~62+1466+

4 Ben-Aft. Y., C~,~rubini. E. mad Rovira, C + Effec+ts of mu ~a~ini¢ and ~po~+dexuL~ and somatic field po~enfia|$ recorded sirf uitaneou$ty ia lhe rat ammeters ham in vivo, L PhysieL (Land .)+ in pre~+.

5 t~en-Ari, Y++ Kr~ajevi~, g.+ Reiffens~ein, R J . and Reinha~d~, W., ln:hi~to~'y ¢o~duet~nce::ehanges and ~¢tien of -~+ami~lebutyra~e in ra~ t~pNxa.mpu~° N~rOge~enee, 6 ~i~"l} 244~=2~3+

6 Ben-Art+ g., Krnjevi~, K., Reiahardi, W+and ~ofmt~ N., ~mraeel~iar 0 ~ of +he+di~nhi~ + i~ery action ~f aee~ylcholine i~ the hir~aeampu~, ~uros.de~e+ 6 (t98+!1 ~ 7 5 ~ 2 ~ .

7 Honnsga~rd, 3., Pre,,+ynaptic'~.' inhibi~or~" a¢l:Joa of acetylcholh~e in area cA~ ef ghe hi6~eampu~, Exp. Neuroi.. 62 i i97g} 797+797.

8 Kan~el0 E.R°, Spencer, W.A+ am~ Nin]ey+ F°J+, E 1 e ~ r o ~ o l o g y of h ip~ampal nm~r,~)ns+ I.

9 Krnjevi++ ~+, Reiffe:+sm+++ m~!s h~ppocampus: e~mce~ula~

IO Va~entino+ R.J+ aa~ L~4n the hippeeampus, J~ Neurosci,, I (1981) 784-79L