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Effects of stimulation of the frontal cortex on identified output VMT cells in the rat
Nemoec/eace/.aette~ 15 (1979) 103--107
103
© glmvier/North-Holland Scientific Publishers Ltd.
EFF]gC~ OF ~ T Y O N OF THE FRONTAL CORTEX ON ID]gNqq]FIBDOUTPt~ ~ CELI~ IN THE RAT A~M, THIEILRY, J.M. DENIAU and J. FEGER Labomtof~ de Ph~iolo~e d a Centres Nerue~, Uniuer~~'~Pierre et Marie Curie, 4, f a c e JuBieu, 75230 P ~ Cedcx 05 (France) (Reeei,w~ July 1 ~ , 1979) ( ~ ~ teeeiwed October 2rid, 1979) (.accepted October 4th, 1979)
SUMMARY
The ~ located in the mesencepbalic ventzo-medial tegmentum (VMT) and proje~ing to the nucleus ~:cumbens, the septum end the frontal cortex were i~ntified by the antidxomic activation method. The activityof single VMT cells was extracellularly ~.orded in Ketamine anaesthetized rats. The effectof the ~:mulation of ~ medial frontal cortex on the ac~v~y of them identified V M T cells hembeen s ~ . The main response observed was an excitation ~ was followed in some cases by a depzession of the spontaneous discharge of ~ ~tls.
The ~ h a l i c ventro~_ial tegmevtum (VMT) contains the dopamineq~ (DA) neurone of the Aso gr~dp which project to the frontal cortex end limbic m'ucturm [3,1Z]. Recent e~ect~phyJ~iok~c~ and anatomical [2,4] studies suggest that there exist in addition non-DA VMT p~ojections to the fi~mtal cortez, the nucleus m~anben~ m~d the septum. A ~ PrO'~ection from the ~ t a l cortex to the VMT hew been demonstrated histologicatty,eitherby the rank Heim~ ~ IS] or by ~ o g ~ e [10] cr ~ m ~ [I] ~ techniques.From these ar~tomical data and from behavioral itudim [9~11] it can be supposed tbz~ the fronted cort~ may modukte the ~ of the me~limbic and m e m c ~ systems. The p~" ~ible con~ol be V M T neJ~ons s e p t ~ or the
~ b e ~ ~ t~e
fo~mg
~ ~ e s
9650 ~m, L, I ~ , c ~ was ~
acc~
~ the atlas of K S ~ and ~ippel |7]:
H, -1 ram). The medial ~ of the ~ ~nCal ~ ~ o moaopol~ ~ (160 ~ m diameter)
tip, at the f o ~ e~onlinat~ (A, 10,300 ~m; ~ 0.8 ram; H, + I ~ mm A, 11,300 ~m; L, 0.8 ~ m ; }L + 1.8 ram). ~ ~mnuli ~ ~ d ~ i n ~ squa~wave ~ of 7 ~ - 2 5 0 ~A ~ ~ 0.2--0.5 ~ "~ The acC~v~ of ~v.gleV~eI' calls waJ ~traae~uI~ly ~ wi~ ~ ~ p~pe~.~s f ~ w ~ p o ~ sky blue ~ e d l in 1 M KCL The form of the ~ike and the ~ of ~ ~ ~ ~ ~ ~ ~e~ to diffe~r~i~e ce~ soma &~m fiber ~ The ~ - T ~ ~ ~ p~oje~h~g to the nudeu~ ~ , ~ep~ua and h ~ t a l ~ by the c ~ e n o n of a n t ~ o n d c ~ ~ n following ~imul~i~n intheseva~ioua Spike poCen~ia~ were c o ~ e d to be ~ ~ evoke~ when ~hey had a fixed latency, followed h ~ f~luency ~ t i m ~ n and collided~ spontaneous spike~ at an iater~a] close to ~ sum of ~ ~e ~ of the evoked spike and the refractory perk~ of the ~ m u l ~ v d ~ o ~ The of anfidmmic~y~evoked ceils was ~ v e ~ by ~ following the t~phc~etic e~ction of Pont~dne ~ky blue (7 #A cat~odal~ 30 ~ ) . T ~ of the gimulafion e~ec~ode tip was verified ~ ~ y by marking the t i ~ e at the end of the ~ i n g ~ ~ e~ly~ ~ of (20 ~ A ~od~, 20 ~.) ~ o ~ by ~ ~ ~ the ~ , ' ~ ~ ~ e ~ep~um (N ~ 40),the nu~eu~ ~ ~ (N ~ 19) (Ylg,I) or ~ I ~ ¢ ~ cotter~ (5/~ 25). The lat~acy of the ~ d t o r a ~ ~ ~ed ~ d~tribution of 1.5~32 maec for ~ ~ p i ~ , 1 , ~ 1 ~ f ~ ~ r~uel~ accura~as and 2-40 ~ for the f r o n ~ c ~ , ~ ~ t ~ g e of ~t~cie~ correspond, as d ~ ~~ly [4], ¢¢ ~ ~a~idmudc a ~ i o n of f ~ t and slowly conducting fib~ta. Moa¢ of ~ ~ cells ~ e d ~ ~aulation of the frontalc¢~¢¢e~.~ ~ p o n a ~ could be c ~ . e d int~ two maior Wpe~: (i) an excitation (N = 49} in ~ cues f~li~wed ~ an i a h i b i t ~ ~riod; (ii) an inhibition o f ~ ~ t ~ t ~ ~ (N= 25). E~dta~ory re~pon~. SCh~aul~icm of ~ ~ ~ h~uced ~ e~ciCa. tion of VMT n e u ~ projectir~g ~ Che ~ (N = 31}, ~ ~ u d e ~ accuraber~ (AT= 9) (Fig. i) or ~ ftoaCal ~ (AT= 9). T]~ ~ c ~ (means and S.E.M.) of the~e ~ v , ae~ were 14.5 ± 3.9 ~ , ,14.0 ± 3.4 and 14.2 ± 3.8 mae~ re~pec'Civeiy. These e~,i~toey ~ were o ~ e ~ e d on both ~owly and fa~ c~nducth~ ~ neum~ m~er~ ~ different areas and shaze the followings i m i ~ c ~ ¢ i ~ : (i) The ~ t , ~ ms p o ~ c~uld be induced by a single ~timul~ to ~ ~ontal corbel. Under ~ese condi~ons fl~e response generaily c o ~ of only (me ~p~ke. (fi) The probability of ~ for ~ e VMT uni~ was ~ following $timulat~n of the ~ron~ c o r ~ a~ a f~eque~c~~of 5--10/~ec and ~ ¢~m~iderably with s~imulation frequency over 2(}/sec. (iii) The exdtatory r e s p ~ e was
10.5
Fi~ 1. ~ neuron iden~ff~ation as p r o i ~ c t ~ to the nucleus ae~umbens and activated by ~timulafion of ,he frontalcortex. The E~st two columns show the characterization of the antidmmic ~tmponse evoked Iry stimulation of the nucleus aeeumbens (stimulus artefae~ imtleated by white dots). From top to bottom in the fL~st co!urnn: fi~ed latency (lat. 17 ~ ) of evoked ,#kes; coll~on (~) with the s p o n ~ u s spikes ~ e n at the beginning of t ~ trace; recovery of t ~ antMromie activation with a delay ~tween the spontaneous ~pik~ and the ~ t l o n g~eat~ than the s u ~ of th~ latency of th~ anf.idromlc response ~nd the ~efr~e*~zy pe~d. ~ e o a d ~lumn, top to bottom: determination of the refract,ory p ~ i ~ (R.P,) wi~h rel~titive stirtt~!~ ~ t ~ nt~c~u~ aecum~ns. The ~_rrowa indicate ~t~ ~ntldromlc a e t ~ t l o n of the initial aegment, ( ! . ~ D fractionation), Third column, top, show~ o A h ~ ~ivat~ fo|Mwing stim~lation of the frontal ~orte~. Note the *~b~nc. of eo||~Mn with the: spon~neou~ splk~ ~ n at the s~ar~ of the trace and also Lhe ~afiabi|ity of the ~teney of the r ~ , ~$ow i~ a d~gram suggested by this ex~rir~ent. The d o ~ | i ~ between t ~ ~ronta| c o ~ t ~ and ~ T r e p r i n t s a mrOn{)aad/or a polyo ,yt~t~c p~,hw~y.
o#~hodmmic (mono or poIysynaptic) since the latency of the re,porvse w~s variable (4--7 m~ec for a eorticat **imuL~*ionrate of I[~ae} and s i n ~ the s p ~ did not ¢oUide with spoh~aneou, d~harge~ (Fig. 1 ). (iv) The excit~tory respor~es were folowed M ~ m e e ~ by a dent ~fiod whose mean du~t~on ~ 200 rrmec. Inhibitory re~pome~, The other type of ra, p o ~ e i n d u ~ by the stimulation of ~he ~ontat c~rtex was an initia! suppre~i~n of the ~ n t a , ~ o u s fi~ng rate ( l ~ , O / ~ e } of f~e VMT ce~. TI~eae i~hibitory re,'%~on~ were ~'~b~r.,~,ed ~ t h 6 of the ! 9 neuzo~_s pmjee~i~ ~ the ~ueleu~ a ~ u m ~ n ~ and with only 8 Of the 40 ne~on~ p~o~ec~,ing~ the ~p~um, The mean duration of ~heae
106
VMT
V M T cellsp ~ I n ~
to the aueb,~ ~ u ~ a q m m
line between the frontal ecrtex ~
~
~
e~ ~mlal em~cllmM.The dotted
•~
s~l[~ • ~
lath:
wily.
inhibitions was 72 ± 19 msee and 275 ± 106 msee,t ~ t & ~ [ y . T b z t r lstency could not be deter,,,;,ed seeurmW beem~ of the ~ spoatmemm firing of the ~ oelb. In the ewe of 16 of the 28 VMT nemmm identified
as p r o ~
to the h . . ~ l oort~ trait, t ~ ~
~
tr~Wnd by
the sthnulation was followod by a dhmt period of 172 t 77 mine. The preaentresu~tarevml tha~ the frontaleor~ez m o d u ~ the ~ of VMT neurons p~oject/~ to the septum, the nucleus seeumbens or the frontal cortex itmlt, as dmc~bad d/qi~ouilksl~y in Pig. 2. Them data lure compat/ble udth the ex/stmu~ of a dwes~lh~ ~ ot~Insi/ng in the front~ cortex and ~ to the V m ' [I,SAO]. ~ ~ of the frontal cortex induced mainly - , ~ of the idultfled VMT eelb, although some inhibitory rmpomes were ~ reemded; ~ effects have been mentioned p.~vioudy by Edinllsr et d. [§]. Most of the inhibitory responses were observ~l on VMT ~ ~ ~ from the frontal cortex. So that the ~ tion o f ~ effes~nts but ~
reepome m ~ no¢ be d m to an e ~ i v ~ to a ~ o f the fl~hog o f the o-.~I (either beesme of ~ ~dbl~.on or
following ant/dromic ~ because of a ~ ~ v e m~actory podod fo0owl~ the antidr~.a/e spike, although the inh/bit/o~ were ~ thoo can be ~ l / l y ~pliM~W~i by this last mechanism), The ~ ~ ~ ~ of ~ of the frontal cortex was m m c d ~ of the VIWI' eegs la'ojeet/q,to the septum, the nucleus accumbem orthe ~ eoetm~itsdf. TJ~ ef~e~ Ires observed on slowly as well as on f a t eouduethq n ~ u s . A~ ~ ~ ~ slowly and fast conducting netuons may corre~md to DA and non-DA mmrom [2,4].
107 I t is interesting t o n o t e t h a t a l m o s t all t h e V M T cells identified as p r ~ jec~..ng t o t h e septum received this e x c i t a t o r y i n p u t . T h e c h a r a ~ c s of t h e e x c i t a t o r y responses ( l a t e n c y a n d f~equency sensKivity) in t h e VMT are similar t o t h o s e pmviousiy described in t h e m e d i o d o r ~ ~ nucleus o f the thalamus a f t e r fzontal cortical s t i m u l a t i o n [ 6 ] . T h e e x c i t a t o r y responses observed in t h e VMT are very l i k e l y t o be i n d u c e d b y activation o f t h e direct corticomese~cephalic projection [ 2 , 8 , 1 0 ] . Howe.~er, our results do n o t allow a conclusion t o t h e m o n o or p o l y s y n a p t i c n a t u r e o f these e x c i t a t o r y ~ p o n s e s . T h u s t h e f~ontal c o r t e x seems to indirectlyinfluencelimbic structures such as the septum and the nucleus accumbens via the V M T . ACKNOWLEDGEMNNT$ This m s e a ~ h was s u p p o r t e d b y D.G.R.S.T. (Grant DNP 69). T h e a u ~ o r s wish t o t h a n k Dr M. Hvadley a n d Dr. J. C l o w i n s k i for their helpful c o m m e n t s o n t h e manuscript. REFERENCT.8 1 ~ , R.M., An auto~diographie examination of cortieo cortical and subcortical pro~etion~ of the medio dorsal projection (Prefrontal) cortex in the rat, J. cornp. N~rol., 184 (1979) 43--62. 2 B~gm', B., Nguyen-Legros, J. and Thierry, A.M.. Demonstration of horseradish peroxidue and flum,Ga~ent catecholaminea in the same neuron, Neurosci. Lett., 9 (1978) 297--302. 3 ~hmd, A. and LindvalI, O., The me~-tvlencvphalic dopamine neuron system: a r ~ t ~ v of itt a ~ . In K.K L i v l n ~ n e and O. Hornykiewicz ( F~is.), Limbic Mec. han~ Menum, 1978, pp. 80"/--331. 4 ~tau, J~., ~ , A.M. and Feger, J., Electrophysiologicai identification of ~haii¢ v e n t r o ~ i ~ tegl~ntal ( V ~ ) ~ u r o l ~ projecting to the frontal ~ , ~m ~d n ~ accu~ B r ~ Re~, in p r ~ 5 E~|' g~, H.M., ~ , $,Z. and ~ i , A., Effect of hypothalamle stimulation on ~ , Lsrp. Neurol., 54 (1977) 91--103. 6 i~dltn~r, H.M., Siegel, A. ~ Trola.~Jo, R., Effect of attmulaLion of prefontal cortex aBd amygdala on d ~ i ~ l t v neuroluh ~ i n ~ , 97 (1975) 17--31. 7 ~ J,F.R. aml gltppel, R.A., The r~ttbrain: a ~ e o t a x i ¢ atlas, K_deger, Lluntir~ton, Pew Yock, 1970. 8 I~m~azl, O.H., The p r e f o ~ l cortex of the rat. I ~ Cortical projection of the medio domfl n ~ lI-- Efferent e o ~ n ~ Brain ~ , 12 (1969) 321--343. 9 LN~lllps,A.G. and F | b i ~ , A.C., The role of dopamine in maintaining intracranial • ~f~mul~tton in tlw ~ t r a l ~ t u n , nucleus aecumbena and medial prefrontal ¢ort~, CereS. J. l~¢hol., 32 (1978)~8-~6. 10 I v a n - - , O.T., ~ t pt~ectiom~ to A10 dopamine~c neurons in the eat as by the ~ ~ of ~ i ~ pvroxidMe, Nettro~. Lett., 9 (19"/8) 35S-,"-359. 11 R m ~ a m f , A. and t~mto~Andemon, R ~ . , The ~ t c a l role of prefro~ta! cortex in i n ~ ~ l f - ~ m l a t k m : ~ ~ history of a n a t o ~ l localization o~"motivational l ~ y ~ u l m ~ e o k ~ g ~ , ~ u ~ , ~ v Yo~k, 1977. pp. 11'-'24. 12 U ~ , U., ~ e o t ~ ~ . n g of the mono-amir~ pa~h~y~ in the ~at h~rsin, Ae~a p h i L ~ m d . , Supp~ 367 (1971) 1--48.
103
© glmvier/North-Holland Scientific Publishers Ltd.
EFF]gC~ OF ~ T Y O N OF THE FRONTAL CORTEX ON ID]gNqq]FIBDOUTPt~ ~ CELI~ IN THE RAT A~M, THIEILRY, J.M. DENIAU and J. FEGER Labomtof~ de Ph~iolo~e d a Centres Nerue~, Uniuer~~'~Pierre et Marie Curie, 4, f a c e JuBieu, 75230 P ~ Cedcx 05 (France) (Reeei,w~ July 1 ~ , 1979) ( ~ ~ teeeiwed October 2rid, 1979) (.accepted October 4th, 1979)
SUMMARY
The ~ located in the mesencepbalic ventzo-medial tegmentum (VMT) and proje~ing to the nucleus ~:cumbens, the septum end the frontal cortex were i~ntified by the antidxomic activation method. The activityof single VMT cells was extracellularly ~.orded in Ketamine anaesthetized rats. The effectof the ~:mulation of ~ medial frontal cortex on the ac~v~y of them identified V M T cells hembeen s ~ . The main response observed was an excitation ~ was followed in some cases by a depzession of the spontaneous discharge of ~ ~tls.
The ~ h a l i c ventro~_ial tegmevtum (VMT) contains the dopamineq~ (DA) neurone of the Aso gr~dp which project to the frontal cortex end limbic m'ucturm [3,1Z]. Recent e~ect~phyJ~iok~c~ and anatomical [2,4] studies suggest that there exist in addition non-DA VMT p~ojections to the fi~mtal cortez, the nucleus m~anben~ m~d the septum. A ~ PrO'~ection from the ~ t a l cortex to the VMT hew been demonstrated histologicatty,eitherby the rank Heim~ ~ IS] or by ~ o g ~ e [10] cr ~ m ~ [I] ~ techniques.From these ar~tomical data and from behavioral itudim [9~11] it can be supposed tbz~ the fronted cort~ may modukte the ~ of the me~limbic and m e m c ~ systems. The p~" ~ible con~ol be V M T neJ~ons s e p t ~ or the
~ b e ~ ~ t~e
fo~mg
~ ~ e s
9650 ~m, L, I ~ , c ~ was ~
acc~
~ the atlas of K S ~ and ~ippel |7]:
H, -1 ram). The medial ~ of the ~ ~nCal ~ ~ o moaopol~ ~ (160 ~ m diameter)
tip, at the f o ~ e~onlinat~ (A, 10,300 ~m; ~ 0.8 ram; H, + I ~ mm A, 11,300 ~m; L, 0.8 ~ m ; }L + 1.8 ram). ~ ~mnuli ~ ~ d ~ i n ~ squa~wave ~ of 7 ~ - 2 5 0 ~A ~ ~ 0.2--0.5 ~ "~ The acC~v~ of ~v.gleV~eI' calls waJ ~traae~uI~ly ~ wi~ ~ ~ p~pe~.~s f ~ w ~ p o ~ sky blue ~ e d l in 1 M KCL The form of the ~ike and the ~ of ~ ~ ~ ~ ~ ~ ~e~ to diffe~r~i~e ce~ soma &~m fiber ~ The ~ - T ~ ~ ~ p~oje~h~g to the nudeu~ ~ , ~ep~ua and h ~ t a l ~ by the c ~ e n o n of a n t ~ o n d c ~ ~ n following ~imul~i~n intheseva~ioua Spike poCen~ia~ were c o ~ e d to be ~ ~ evoke~ when ~hey had a fixed latency, followed h ~ f~luency ~ t i m ~ n and collided~ spontaneous spike~ at an iater~a] close to ~ sum of ~ ~e ~ of the evoked spike and the refractory perk~ of the ~ m u l ~ v d ~ o ~ The of anfidmmic~y~evoked ceils was ~ v e ~ by ~ following the t~phc~etic e~ction of Pont~dne ~ky blue (7 #A cat~odal~ 30 ~ ) . T ~ of the gimulafion e~ec~ode tip was verified ~ ~ y by marking the t i ~ e at the end of the ~ i n g ~ ~ e~ly~ ~ of (20 ~ A ~od~, 20 ~.) ~ o ~ by ~ ~ ~ the ~ , ' ~ ~ ~ e ~ep~um (N ~ 40),the nu~eu~ ~ ~ (N ~ 19) (Ylg,I) or ~ I ~ ¢ ~ cotter~ (5/~ 25). The lat~acy of the ~ d t o r a ~ ~ ~ed ~ d~tribution of 1.5~32 maec for ~ ~ p i ~ , 1 , ~ 1 ~ f ~ ~ r~uel~ accura~as and 2-40 ~ for the f r o n ~ c ~ , ~ ~ t ~ g e of ~t~cie~ correspond, as d ~ ~~ly [4], ¢¢ ~ ~a~idmudc a ~ i o n of f ~ t and slowly conducting fib~ta. Moa¢ of ~ ~ cells ~ e d ~ ~aulation of the frontalc¢~¢¢e~.~ ~ p o n a ~ could be c ~ . e d int~ two maior Wpe~: (i) an excitation (N = 49} in ~ cues f~li~wed ~ an i a h i b i t ~ ~riod; (ii) an inhibition o f ~ ~ t ~ t ~ ~ (N= 25). E~dta~ory re~pon~. SCh~aul~icm of ~ ~ ~ h~uced ~ e~ciCa. tion of VMT n e u ~ projectir~g ~ Che ~ (N = 31}, ~ ~ u d e ~ accuraber~ (AT= 9) (Fig. i) or ~ ftoaCal ~ (AT= 9). T]~ ~ c ~ (means and S.E.M.) of the~e ~ v , ae~ were 14.5 ± 3.9 ~ , ,14.0 ± 3.4 and 14.2 ± 3.8 mae~ re~pec'Civeiy. These e~,i~toey ~ were o ~ e ~ e d on both ~owly and fa~ c~nducth~ ~ neum~ m~er~ ~ different areas and shaze the followings i m i ~ c ~ ¢ i ~ : (i) The ~ t , ~ ms p o ~ c~uld be induced by a single ~timul~ to ~ ~ontal corbel. Under ~ese condi~ons fl~e response generaily c o ~ of only (me ~p~ke. (fi) The probability of ~ for ~ e VMT uni~ was ~ following $timulat~n of the ~ron~ c o r ~ a~ a f~eque~c~~of 5--10/~ec and ~ ¢~m~iderably with s~imulation frequency over 2(}/sec. (iii) The exdtatory r e s p ~ e was
10.5
Fi~ 1. ~ neuron iden~ff~ation as p r o i ~ c t ~ to the nucleus ae~umbens and activated by ~timulafion of ,he frontalcortex. The E~st two columns show the characterization of the antidmmic ~tmponse evoked Iry stimulation of the nucleus aeeumbens (stimulus artefae~ imtleated by white dots). From top to bottom in the fL~st co!urnn: fi~ed latency (lat. 17 ~ ) of evoked ,#kes; coll~on (~) with the s p o n ~ u s spikes ~ e n at the beginning of t ~ trace; recovery of t ~ antMromie activation with a delay ~tween the spontaneous ~pik~ and the ~ t l o n g~eat~ than the s u ~ of th~ latency of th~ anf.idromlc response ~nd the ~efr~e*~zy pe~d. ~ e o a d ~lumn, top to bottom: determination of the refract,ory p ~ i ~ (R.P,) wi~h rel~titive stirtt~!~ ~ t ~ nt~c~u~ aecum~ns. The ~_rrowa indicate ~t~ ~ntldromlc a e t ~ t l o n of the initial aegment, ( ! . ~ D fractionation), Third column, top, show~ o A h ~ ~ivat~ fo|Mwing stim~lation of the frontal ~orte~. Note the *~b~nc. of eo||~Mn with the: spon~neou~ splk~ ~ n at the s~ar~ of the trace and also Lhe ~afiabi|ity of the ~teney of the r ~ , ~$ow i~ a d~gram suggested by this ex~rir~ent. The d o ~ | i ~ between t ~ ~ronta| c o ~ t ~ and ~ T r e p r i n t s a mrOn{)aad/or a polyo ,yt~t~c p~,hw~y.
o#~hodmmic (mono or poIysynaptic) since the latency of the re,porvse w~s variable (4--7 m~ec for a eorticat **imuL~*ionrate of I[~ae} and s i n ~ the s p ~ did not ¢oUide with spoh~aneou, d~harge~ (Fig. 1 ). (iv) The excit~tory respor~es were folowed M ~ m e e ~ by a dent ~fiod whose mean du~t~on ~ 200 rrmec. Inhibitory re~pome~, The other type of ra, p o ~ e i n d u ~ by the stimulation of ~he ~ontat c~rtex was an initia! suppre~i~n of the ~ n t a , ~ o u s fi~ng rate ( l ~ , O / ~ e } of f~e VMT ce~. TI~eae i~hibitory re,'%~on~ were ~'~b~r.,~,ed ~ t h 6 of the ! 9 neuzo~_s pmjee~i~ ~ the ~ueleu~ a ~ u m ~ n ~ and with only 8 Of the 40 ne~on~ p~o~ec~,ing~ the ~p~um, The mean duration of ~heae
106
VMT
V M T cellsp ~ I n ~
to the aueb,~ ~ u ~ a q m m
line between the frontal ecrtex ~
~
~
e~ ~mlal em~cllmM.The dotted
•~
s~l[~ • ~
lath:
wily.
inhibitions was 72 ± 19 msee and 275 ± 106 msee,t ~ t & ~ [ y . T b z t r lstency could not be deter,,,;,ed seeurmW beem~ of the ~ spoatmemm firing of the ~ oelb. In the ewe of 16 of the 28 VMT nemmm identified
as p r o ~
to the h . . ~ l oort~ trait, t ~ ~
~
tr~Wnd by
the sthnulation was followod by a dhmt period of 172 t 77 mine. The preaentresu~tarevml tha~ the frontaleor~ez m o d u ~ the ~ of VMT neurons p~oject/~ to the septum, the nucleus seeumbens or the frontal cortex itmlt, as dmc~bad d/qi~ouilksl~y in Pig. 2. Them data lure compat/ble udth the ex/stmu~ of a dwes~lh~ ~ ot~Insi/ng in the front~ cortex and ~ to the V m ' [I,SAO]. ~ ~ of the frontal cortex induced mainly - , ~ of the idultfled VMT eelb, although some inhibitory rmpomes were ~ reemded; ~ effects have been mentioned p.~vioudy by Edinllsr et d. [§]. Most of the inhibitory responses were observ~l on VMT ~ ~ ~ from the frontal cortex. So that the ~ tion o f ~ effes~nts but ~
reepome m ~ no¢ be d m to an e ~ i v ~ to a ~ o f the fl~hog o f the o-.~I (either beesme of ~ ~dbl~.on or
following ant/dromic ~ because of a ~ ~ v e m~actory podod fo0owl~ the antidr~.a/e spike, although the inh/bit/o~ were ~ thoo can be ~ l / l y ~pliM~W~i by this last mechanism), The ~ ~ ~ ~ of ~ of the frontal cortex was m m c d ~ of the VIWI' eegs la'ojeet/q,to the septum, the nucleus accumbem orthe ~ eoetm~itsdf. TJ~ ef~e~ Ires observed on slowly as well as on f a t eouduethq n ~ u s . A~ ~ ~ ~ slowly and fast conducting netuons may corre~md to DA and non-DA mmrom [2,4].
107 I t is interesting t o n o t e t h a t a l m o s t all t h e V M T cells identified as p r ~ jec~..ng t o t h e septum received this e x c i t a t o r y i n p u t . T h e c h a r a ~ c s of t h e e x c i t a t o r y responses ( l a t e n c y a n d f~equency sensKivity) in t h e VMT are similar t o t h o s e pmviousiy described in t h e m e d i o d o r ~ ~ nucleus o f the thalamus a f t e r fzontal cortical s t i m u l a t i o n [ 6 ] . T h e e x c i t a t o r y responses observed in t h e VMT are very l i k e l y t o be i n d u c e d b y activation o f t h e direct corticomese~cephalic projection [ 2 , 8 , 1 0 ] . Howe.~er, our results do n o t allow a conclusion t o t h e m o n o or p o l y s y n a p t i c n a t u r e o f these e x c i t a t o r y ~ p o n s e s . T h u s t h e f~ontal c o r t e x seems to indirectlyinfluencelimbic structures such as the septum and the nucleus accumbens via the V M T . ACKNOWLEDGEMNNT$ This m s e a ~ h was s u p p o r t e d b y D.G.R.S.T. (Grant DNP 69). T h e a u ~ o r s wish t o t h a n k Dr M. Hvadley a n d Dr. J. C l o w i n s k i for their helpful c o m m e n t s o n t h e manuscript. REFERENCT.8 1 ~ , R.M., An auto~diographie examination of cortieo cortical and subcortical pro~etion~ of the medio dorsal projection (Prefrontal) cortex in the rat, J. cornp. N~rol., 184 (1979) 43--62. 2 B~gm', B., Nguyen-Legros, J. and Thierry, A.M.. Demonstration of horseradish peroxidue and flum,Ga~ent catecholaminea in the same neuron, Neurosci. Lett., 9 (1978) 297--302. 3 ~hmd, A. and LindvalI, O., The me~-tvlencvphalic dopamine neuron system: a r ~ t ~ v of itt a ~ . In K.K L i v l n ~ n e and O. Hornykiewicz ( F~is.), Limbic Mec. han~ Menum, 1978, pp. 80"/--331. 4 ~tau, J~., ~ , A.M. and Feger, J., Electrophysiologicai identification of ~haii¢ v e n t r o ~ i ~ tegl~ntal ( V ~ ) ~ u r o l ~ projecting to the frontal ~ , ~m ~d n ~ accu~ B r ~ Re~, in p r ~ 5 E~|' g~, H.M., ~ , $,Z. and ~ i , A., Effect of hypothalamle stimulation on ~ , Lsrp. Neurol., 54 (1977) 91--103. 6 i~dltn~r, H.M., Siegel, A. ~ Trola.~Jo, R., Effect of attmulaLion of prefontal cortex aBd amygdala on d ~ i ~ l t v neuroluh ~ i n ~ , 97 (1975) 17--31. 7 ~ J,F.R. aml gltppel, R.A., The r~ttbrain: a ~ e o t a x i ¢ atlas, K_deger, Lluntir~ton, Pew Yock, 1970. 8 I~m~azl, O.H., The p r e f o ~ l cortex of the rat. I ~ Cortical projection of the medio domfl n ~ lI-- Efferent e o ~ n ~ Brain ~ , 12 (1969) 321--343. 9 LN~lllps,A.G. and F | b i ~ , A.C., The role of dopamine in maintaining intracranial • ~f~mul~tton in tlw ~ t r a l ~ t u n , nucleus aecumbena and medial prefrontal ¢ort~, CereS. J. l~¢hol., 32 (1978)~8-~6. 10 I v a n - - , O.T., ~ t pt~ectiom~ to A10 dopamine~c neurons in the eat as by the ~ ~ of ~ i ~ pvroxidMe, Nettro~. Lett., 9 (19"/8) 35S-,"-359. 11 R m ~ a m f , A. and t~mto~Andemon, R ~ . , The ~ t c a l role of prefro~ta! cortex in i n ~ ~ l f - ~ m l a t k m : ~ ~ history of a n a t o ~ l localization o~"motivational l ~ y ~ u l m ~ e o k ~ g ~ , ~ u ~ , ~ v Yo~k, 1977. pp. 11'-'24. 12 U ~ , U., ~ e o t ~ ~ . n g of the mono-amir~ pa~h~y~ in the ~at h~rsin, Ae~a p h i L ~ m d . , Supp~ 367 (1971) 1--48.