i · 246 sometimes also received degenerating boutons originating from neurones in the nucleus...

..... ~ •. m(I .. llld ... W '" Cl a..;../NOfl ...... oII.00d .i_ ... I ...... MONOSYNAPTIC INPUT FROM THE NUCLEUS ACCUMBENS-VENTRAL STRIATUM JtEG10N TO RETltOGRAOELY LABELUD NIGJtOSTRlATAl NEURONES

P. SOMOCiYI.I. f . IIOL .. I\j. S. Torr£AOEu. ,...! .. O. SMIT H'

/" "'_,_, _/ "_T. s-hoWO' _"'T U ..... ~ . ........ / I(_T) _ 1".DoS I U"_."y tN_,_,u -r' .... _~I. S-~ , ... t, '..t. (J4-IO:1I1QT (U X.)

(.l<c<<!'I<om (edOO .1cct.oI)otiG o. by ,njOCtion of UIlnic: acod) i~ an Im. 'ndud;", lhe n..clous aa:umbus.nd part oI . he ven",1 IInll", .. 'n (~~ ra t . ,he ip"~1 to .. J ... t...tan"a n, P'& ...., Jtud;al ,n ,he d.ct,OI'I Microscope.. Dc,eMnti", .10~' .nd "er"" I.e<m.n.l. were fou~d ,"inly in ,he.<>NI ,e",,"t.u...,d ,n 'he ""nu.1 11,.,' 0I.1te :rono _pa.cu O"' .... iUin' synapti.c bou ."", _re (o¥nd '" «)flUe! "",h ... U bodies (.ym .... 'nc 'yuP\o<s) Ind <lend"'<, ( .... 'nly S)'m ..... t .... WI • re'" liIym ..... ""')

The pO<t.ynllMic:. ta'l"l 01 some of the .lrcrml ibru from ,he .... umben ..... "· 1f.1 ...... "'" ..... Cl<&1>IWood by de ....... ",.,,", de ........ I .. '! oy .. p1ic boII'o,,. 01 ,he Abo ... typu '" COflrw ,,"'ILh niJfO$lnarar ... u.t>MS ",tIicb ha<! bct'n id<"ul\cd by r,," Ict.",.adC tn.nSpOrl o! loonc .. dtSk P"'o~'~~ (KRP) (.om I .... main body o( lhe ""atum. Some of I .... IIR P. I,bellf;d ... 11$ _re .Isq ,mpre,nalcd by 'M GoI&l ,u'n aftd de ..... r.ulll boIIlOt\J were found 1ft coelac\ with lhelr d" 1I1 dend",". W. also obsuYed IwO 'ypCO of H RP-<:onU'n"" boUIOI'I' (Pfnumli>ly Labelled 1"le'O«,ld.ly) ... lhe ... MUm •• "' .... after rnjcetion ofHRP into tile ~,~ body of' .... stri.tum' lyIX I bo\rlon.conll .... d I .... Ip/>c" ... l .... iclcs, and fo.med oymrm,ncAl .)napou mainly "" deAd"I'" shoflJ 1ft tbt. ton. ~tiwlau Ind in onc .u .. the deAd.n. wlI from. "il'o.<"aul ... ~.o .... 1)1'" 1 \IooutDfl' I'I&d plcotnorpb", .nd 11. .... n.d ~ •• tek, and fo .. ned ')'M_Incal 1)'ftOp5U .,.;,h pe.tkary. ud pro .. mal <lend,i, ••. c.p:ciall) ,n ,he ...... co .. ....," The Iolte' Iype of HRp·Labell.d bouton ..... '.cqueody found .n . ynapIM: eoonUct ",ilh the ""JI bod ... of n;,,'os!liA,al ".u.o""" .nd lh. u-me n(u.ofo( '

. T._. o_~,~. __ ._._"'bo_ ."",

246

sometimes also received degenerating boutons originating from neurones In the nucleus 3tcurnbens-ventral striatum.

It is concluded that part o f the strlato-nigra-str ia tal circuit ineludes a mono-synaptic link belween neurones io the ventral striatum- aceurnbens and some nigromia.tal neurones . The possible convergence of input from different regions of the striatum on to sinsle nigrostriatal neu rones is also suggested .

l NTRODUCTION

The in volve ment of the basal ganglia in certain neurological disorders has evoked a large volume of research on the reciprocal connections between the substantia nigra and the nt;osuiatum,·H), Then is evidence that the substantia nigra receives a topogra phically organized projection from the neostriatum with y.aminobutyrate (GABA) and substance P involved as transmi tters. In turn Ihe substantia nigra send s a 10pographicaUy organized projection ( 0 the neostriatum using dopamine and possibly some otber unknown transmitter.

While the details of the complicated lopographie projections betwun the [WO

SlrUClU res Are fairly well undersloodJ·~·I~,U.:U very liute)s known about the conneV. tions at Ihe synaptic level. Since both structures afe composed of several types of neurones, as defined by their conltectivity, it is difficult to establish with conventional morphological methods which neurone type or types 3re the mo nosynaptic largets of the p igrostriafal and striatonigral pathways. Recemly we have developed a method in which the projection a rea of a neurone is determmexi by retrograde labelling Wi th horseradish peroxid ase ( H RP), its morphological characteristics by Golgi staini ng and its input by anterograde degeneralioo of afferent synaptie bouconsl l. Applicauon of this method has revealed that nigrolhalamic neurones receive monosynaptic input from sl(iatonigral fibres:!l . ln the same series of experiments, however, we failed to find monosynaptic input to nigrostriatal neurones from the dorsal neOstriatum in the rat.

Using tbe anterograde transport of radiolabelled proteins ;1 ha~ been demon~Irated that the nucleus atcumbens-ventral stria tal region sends fibres 10 the dorsal substantia nigra inlO, or close to, the area where the cell bodies of nigros.triata l neurones Me IOC3ted S,2UB.I4. To establish if this projection from the ventral part of the striatum terminates monosynaptically on nigrosuiatal neurones, lesionS were placed in the nue1eus accumbens-ventral striatum region prior to injeclion of HRP into the main body of the striatum. EIC(;Cfon microscopic. analysis of the substantia nigra. was the ... carri ed out 10 see whether re n oarade ly HRP·!abeUed nigrostri.ual neurooes receive monosynaptic input from the degenera ting term inals of fibres originating h orn the area affected by the lesions. In the same animals, we bave also sWdied the synapses formed io the substantia nigra by boutons that conta in HRP.

MATERIALS AND METHODS

Ten male Wistar ralS ( 160-1 80 g) were used. All operatioos were performed

under deep c.h1ora! hyd rale anae.slhesia (OA ~ka: i.p.). Three of the raU received unilateral eleclrolytic ~5ion5 (2 mA, 5 sec, anooal) in the ventral striatum- nueleus ac.eumbens rc!ion at eoordmalC:s A, 8.9 , L, \.8 ; ventral S.2 mm from the pial surface aocord l n~ 10 K6nig and K.lippe.lll i 0.2 mm of the dec.t rode tip was free of insulation . Four other fats received an injection of !:::time acid (I ~, s,!ma, 40 nl dellyered during 10-15 m:n) in the same era. One or two days laler all r:l.1$, excepl one of the: ka inic acid treated lJIimals, received an injection of -40-50 nl HRP (20y' in waler, Sigma type VI) into the .striatum ipsilueral to the ksion at (;()Ordina tes A, 7.5 : l, 2.5; venlra1 4.S mm from thc pial surface. A 1\ injeCllons were deli vered as described prcvlouslySI using glass capillaries with t ip diameters of aboul 50 .um. A frer the appropriate survival lime the aninlals were per(used through the heart wi th a fi xati ve of 2.S % SlufarA ldehyde, 0.5i{ paraforma ldehyde in 0. 1 M sodiu m phosphue buffer, pH 1.-4JI.

The brain was removed (rom the sk ull and immersed in the $.Ime fixative for a further 3 h be fo re blocks ..... ere dissected. From the fortbrain 40 ~I m sections wele cut on a cr)'50stat and one ser;e.s was processed fo r Ni ssl stai ning and anoc her to loca lize the HRP injection site using: o·(o\idine O,3'·,IiIn~lhylblm:idin~) as substr.te31 • Some blocks containmg the substantia ni,ra were processed by the Golgi-HRP Irans· porl-de@t!ne ra lion proctdure described previously'l . Some other blocks from ( .... 0 HRP injected anima ls and blocks (rom the kainic acid injected animal whIch did not receive HRP injection wtre sectioned at 50 p.m on a SOfVall re-2 !ISsue chopper. These section.s were washed overnight in 0 I M sodium pl'aospht le bufJ'er (p H 14) and incubated (Ot 30 min . .I.t room lemperature, to reveal H RP activity using 3,3'.diaminobenZldint; (DAB) as substrate in a procedure s1i,hlly nlodified from lhat of G raham and Karnovsky'. T he incubation media contained 0.05% DAB (teuahydrochloride , SI,ma), 0.0 1 y. Ht~ in 0. ' M .sodium phosphate bu lfer al pH 1.4. Some sections were incubaled in a medium from which either the DAB or the Hlea was omitted . After incubation the sections were washed in IWO changes of buffer ror 30 min, po.slfixed In 2Y. O.sO .. in 0.1 M .sodium phosphate buffer (pH 7.4) for 2 h, deh)'drated and embedded in Araldite (Durcllpan ACM Fluka).

AOer evalul.lion of the mjeclioJ1 sile. the retrograde tranSport of H RP, the utent of the lesion caused in the ven lnl striatum-nucleus ac.cumbens region and the an tcroarade degene ration detectable in lne substanlia nigra , 3 anima ls were selecled (or the present report (F i~ . 1). The I.nilTlllllabel led ST24 received kainicflcld and , 49 h I.ter, HRP j it was killed a.rter a fu rther 17 h. The IInimal labclled S'[27 rece i ... ed all electrolytiC lesion and HRP at the same mlervals before death as ST24. The animal la belled ST2S received kainic acid and, 18 h later, H RP ; it waS killed a fu:r a rurt her 22 h.

Semi thin sections ( I I,m) wel'e cut from the .subslanlia nisra 10 del.c:cll'etrog rade labcllini and ult rathin sections from the area of retro,rade labell ing wefe uamined for deae nerati" g boutons in fhe electron microscope. Areas wit h both retrograde HRP·labelling and aAterograde degeneration were then ~ctioned Kn ally for electron microscopy. The followi ng: num ber or areas were studied : cue ST2-4, S areu (out or6 examined). case ST21, 2 areas (5 examined), ase 5T28, 2 areas (l eummed). In addition one block. was studied from the contralateral .su bstantia nigra from aOlmals

I

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252

NM

Fig. 4 : Camera lucida drawing of lhoe 5 HR?· 'abdled. Golgi s .~ned nivoslrialal neuroots in .~ 20'" comp.;lcta (SNC) or the subslamia nigra showJl in Fii. 1. The positions or HRP·Jabc:ltcd neuronc.s (60Is) and or Golgi sra ined HRP-Iabt.lled neurons (!.qu.tu) arc stlown in the inKI. Neurone number one was round 10 receive IWO degeneratinl boulons from the nudeu! accumbeM-vet\lral Slria tum resion (SIMS) on iu dcndril t . I. axon ini t l.11 stiment; Aon, accessory optic nucleus; LM, mediloJ lemniscus: NM. nucleus mamillatis; SNC, substa mia "lira zona com pacta ; $NR , $ubSlanlia nigra_zona rct iculal3. Scales: drawing. SO pm : i n~t. 0.5 mm.

#m sections the DAB reaction end-product appeared as black granules in the neurones while Ihe reaction end-product formed from to!id ine was brown and was found both in granules and di ffu sely in the cytoplasm (Fig. 3a and b). At the electroD microscopic level the reaction end-product formed from DAB was highJy electron dense. Jt was

FiS. 5. Several boutons containing l&.rge round clur synaptic Yesicles make sYMptic Contlct (la rge arrows) wi th a dendrite in the zona reticulata or the substantia n;srl. Two of the boutons (type t) contain HRP reaction end-procluct {hori.wnt l] arro ..... s). Note prominent presynaptic dense projcelions, long .!.ynap.ic ac tive zones and slight postsynapt ic membrane specia liza tio n. Idv, large del\$C core vesicles. Case ST24, DAB as substr&te.. Scale ror figs. 5-8,0.2 }1nl.

Fig. 6. ~generllling bouton (db) in the zona reticulala is seen to make synapdc contlct (large arrow) wi th a dendritic shaft Id). The bouton, as well as another normal bouton (star). also COnta iM HRP reaetion end·product in membrane limited .!.tructures (horizon t31 a.rrows}. Case ST24, DAB u substrate. Fig. 1. Golgj·mioe<l, ,old toned bouton Or;) local axon collateral in the striatum origin.uing rrom a stria tonignl neuron. ~ boulon conlaining large clear vesicles makeJ a synApse (b.rge arrow) with a dendritic shaft (d). long arrows indicate sold partieles. Fig. 8. Synaptic conUlct (Iuse arrow) between an HRP·labelled (hor il ontalarrows) type 2 bouton ant; the perikaryon (P) or a zona compacta neurone in the substantia niif2. wbich was also HRP-laIxU~d relrO&l1tcely ('rom the SlriJlUm. Case 5T27. DAB as subs.,a te.

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TIoo .,....,. .. _ .. 0# d ..................... ,. _Id loO .... bliPod .. .... loo .. 01 , ..... ~ <loft Oftd .... pool''''''",", _ .... _~_. 4, , ....

.... ocb ... _ ....... ''''''1 .. 11 = ...... ",IIt .rya...n _IS of~.

"' _toy.'pIO< <1< .... m .. ~ri. ' "". Id bo ...... " .«1 (Fill 1< 'nd l id). ~O", 'PP"';""" of !I." 'l"";>tJC .... ....". ..... "';, h ... ocIu1.I< _1'fI~ ....... " <ouI1.;' ubi< (F.,.. ,."" 100\ .. tilt dri)' ....... 01 .sqe •• cn.u"n. , ... re <a$C$ "ri, ""d aI ~,,,,,,,,,,., bo.'<HII "';, 11 I~ I <11."",.,.;"", _re rO""" '" co.", i. 11 RP .... '''". <nd'prod"Cl on ,.b.l .. <>1 , moolll o.dopl .. m,. ffl.cu'.m (Fi , 6) In odd,,,,,,, !(' 'he ,_"ca' IYI>< 01 ",,_ •• tinS .... " ... Oft ".nury> &1>11 de""n .... a r. ... "" d .. d. [o< d. ,.."" ,., boo,,,,, . ...... fooBd. ~'"h .... n"" .,y",,,..,,i. typt ]><>". 'y,,"poic """"Y S,..."k N)oIt'~tIl. J "'''''"'''

In .- ...... ,, "" ... Ilroc ...... or d.,. .......... o_1lA><d ............ ,d,,," '_1 .. bel ......... fOo($ _Uf'n,". nu""",OOO .~ri<.ol 'yo)l.pt'" .... , .... be, ...... ,11, ]><,i t o'\'I of "'Itoot'; .... , no"ro •• , .... d ..... , .. i.1 "" ...... '.,.re r.,.,od (F.,. . l . ..... "1_ I ...... -..oa "1' '0 do ...... 'rnapr .. <0 ...... _. olMoNed "" I ...... MU' ...... I)<ftd,,,,,, <o. tai., •• H RP·, .. ",io •• "d.procl~" .1.., 1<C< 'vtAl de •• ".,; •• " "" ' ........ d <>« .... ,0 •• 111 .. ,..,al "'",ne<al1., bo.,,,,,. <0 ..... 11«1 o" ' ~ OIl< HltP· labelle<l <lMdr"lre (Fi. IG).

0 . . .... "0'" u;"'., S114 "h,ch co.tained S H ItP·I.b<II,d 0<1" 'h" ' .. " "'" GolJj ..... r"oOd ........... ;.d u."" tl>< ........... _'OS<Opt (Fi,.. ).nd4~ Oqo .... . ,,""

,. ,hr .... ''''' _ . "_ ...... 'h< lOO< of ........... hon >lOp"'" oil"" of 'h< pt""')'>. 0.11 'wo dt ....... , ' •• bou,o .. w,,, found in .,n,,,. ;< ""." '" w;,h ,h. (;<>15' " . ,""'. ,old """,d de ..... ,iu of "'" of 'h< H RP.lal>o:ltd ni" ... ,,,,, .............. (N, ,n Fip. ) ..... 01) •• I,"" •• h "' ... , of ,ho I .... h of ,hr, oJor>dril .. I ..... 11 .. ' h' ",h< .. , ..... "ud"d ,n ... 1., I«';on.

Hltf·"~lod.,,,,,,.-I _ .. , .. ",,,,,,,,

Enlym< ,..,.oUo. ~"".prod"'" w" ..... ""'1 fooOKl 'ft p<ri~.ry •• "., daMI,~ by, w ... 1>0 po'''.' ,n mydo' ... 1ed .. " •• , od . ....... f'''';'''''''''1. in 'h," unw.)'<I", . .... """I. It <0. 1d •••• 11)' be found .... 'h'" m,mb" .. lin,"cd ,ub,'" . od "".ie~ ooo ... i"""lI, in de ... bodie1I"" ",uM;,...;c ..... , _ .... The ............... <WO ' I'P'" 01 ..... .......... 10 """' .. "'". HRP ............ tnd·p'<>od 'h", r;kfId,ili< u..'u .. _11 .. "'~~ 0000",-..1 ....... 01'- & ... drileO (Fi,.. J o.nd 9). The)r ........... d ""I<. d.", ,~OHI .. ~'" w .... h ....... "Ih.'y p.ded ~1I,., "H", of t~ .

bo.,~" (Fi,. l~ " f ... dt ... UK< ud I fI"UW ... odts, 10' ..... '" O;l( ,loo" '110 <In, 0 ..... couklllso be oI>te.-_ i~ 'h<'" ....... ,.,.... The l>oco'OM hd Pfo",_' 'n .. I"~"

'" " . '_ ... _ ....... I<Ilp. .. _ " ...... __ .. _ .......... . F,._ '-'(i".04 to! MO _ " .. _ .... pi"" • .". " (b) , " to). i ..... " ...... " .. {Io'. ' 11"",,)"'_ ,,~r. IoboW {IIoNoM" Of..-} " ... l..,. ......... ... .. , .. ~ ... _. I,. _ ..... , ..... _ '..- .. (.)10 ........ ,.....;._(10' • ...-.)"'~d.,,,,,,_,,,,,,,, _"'oI'; ""', booIr c... !IT". DAI .. ,.100< .. " 5<0 ... ' . , ~ .. , .... . .. d, 0.',.....

pr .. JftOpIJ< <In", prcj " ell no ..... pr .. "" ... <o __ ..... " ....... oM , ........ .. • mO<l<,.,< l'O"syn'pb< _",m ... poa.ol".,,~" (Fi .. 3 •• "). TJ'l'< , boo,,,,,, ... , """,,\COd, • ..c ... ~ _ .. Ia ... 1>< zo •• -.. .. I Fi .. $).

T_ 1 .... _ . Th<x HItP.lobollod bO., ... mod< .>"10 ........ ,b pro" ... ' lI<.d.i, .. bj>, ""i.,y '""~ ""n4<)'O (Fir>- .. JIb ,.:1 11.). , .. , ..... "'''''' (""' ..... Iy f"""" i. , ... _ ..... 1* .... d <on"""" "",,)I .... oo_pIo, ,nd ~'''."...

...,~c1 ... T ... ,,,,,eIt. '«Dm"'.O<d in .""'"0"''' ..... ""'Y'"'PO"""" "' .... "oido __ <OIOporul .. ,_oI'_I_~ TIoo __ powyn~_ ... .".."Iim"'''' ""'''' .",.It .Nl ')'10"'«'""

The .. wo,. d"'I-" ...... in I .. "'~odoood'io ,. , ... 'wo ,~ ""' """'''''' , 'JII'! 1 1>0 ...... "'d .. udo . 1Nl ... &nd _ "",oOoood, .. ,~" '"'" 2 __ (<<HllPO" Fop S ,.d I).

S1"4P'1< "r.",,,,,," ... of H~I'-hl>tll~ " ...... ,..,,,_,, ."",, .... , IUtP·1tbd1<>:l ,...;w, • • ad pro .. ~ delld,_ 0I.~"",,, ... 1 ...... _ f, ••

qIK"o!Y r.oo ..... . , •• .,... (,_ " .. 2 HRI'oI.bdl<d "'''' .... " (1'11 1 I) f. """ .. ",,,,to IIP ' o J lobd:..:! bo_ eould b< ob ....... i. """lOcI .... .., Oft. ".'011< 0.. "'" .,h<, ......... '1P" I lobrilod __ f ........ _,oa"",' ".'-', ",'h ... Iob<\lool dondr~ . ... hO:h P'_'Y "n«" , ... """ ~'I of HRP·l,b<'''d d •• d""" I. lh •• ". o( 'h< zon, .. hallo ........... "", Iob<llod 'l'P000 ...... wo'. ,_.

C. ,,,,,, .. ,,, 01 HItP·I.bdlod "d cIo ..... ", ........ ,"'" .... (",,1><1 OIl '0 ...,.~ , .. , ...... <./)' HRN.b<lIod.<><I """bdl<o1-'''' (Fil 9) .... pr""ty. (r .. 'I) On .... 11< ... , .... 'h< IlkP.bll<llod , ... "., ....... 01,_ I ....... on , ... pu;hty • .... y ..... ', ... l.

C_",." ... 01_ ..... ""'4"",1 "'",IM/,.I """" ... "'.1 .... ,,,..' ,.;,~ 'f'" I Hn· w..JW ........ , I r", $,.J'!

TM boo,"", of 'h< loul .. "" _ ..... 1. of.~ HkP~""1IdI. Golf< ... , ... ...... 01,".1 ""-"_ '0''' ....... itd .",Iu" ,lit ....,...;.'um. T"', .... , .... ..-ot • _, ..... '" <cH ...u. _, ""'1 _, ... , or! .......... tkoc.-.b<rI .......... ,

"f'O"lO. Gold '0.'"' of ,11< (;o~ ".", .. 1 "nllooiarol ... ,on<.nd ~. Iouol .",,, <0110 ..... ' ...... d , ........ ~I dr<t.t~ 0I~, """""<*- Too. bou,_.-._ 100-1<-.......... "' ... "m'b. '" II>ot< in 'Yf>< I .... "' ••• (F'I 7). Th< 1'"" .. ". .. <1< .... projoa_ ~ ....... I do"Ciopod """ , ......... .,.. loaritd '~"'_'ic.ol ,ynopo;c ..,.. , .. .., ""'v"'- 01 , .. 'Jpo I IIRP·lobdlcd bOu .... ,Iy, _re ,_ ...... ,oMt • • ". ", .. i ...... po""" .. ody

O'SCUSSION

J.t_-,-,Ji< ...,'" of "" ....... ,0/ fr/JI .. 0., .. 0,. ~r>d", i. ,~" "'0'0'"'' prOjoffi"1 '" .... ""-01' ....... (,_ ,lot.

"' ...... " .............. _"._ '"9'" ,,"'" .......... '. ,110 ._ .cao_b<r> .. ... ,,,, ..... '"m ,..;0. Tl\.o, , ..... 1[ .... , .. "",oal, <ompo''''. iml>""'" 1""'" of ,loo _ of ........ ""'.! ..... : ............. h, ,he u ... _.d, ...... ' ... __

25'

Oil the perikarya as well as on the pro~imal and distal dendritts. Earlier studies in th ~ rll ' JITld in Ihe eat ll .ll showed Iha1 following large lesIOns in the strialu m degen~at;n8

termina ls could be found;1l synlp!;C C()nlaei with boc.h Ibe dendrites and perikarya o f nia.a! neurones. However, lht ni~ contains neurones that project to many ,)a rts of the brain and 10ClI1 imem eufont$ may OI.lso be present""' . Thus, in lilt; earlie r studies it w.u nOt pouible to determine w;th morphological methods whlcb type(s) of neurOne receive ttle mOf1O$ynaplic afTerenlS from the striatum. Using Ihe retrograde HRP· labeUil'\i or its combination with G olgi staining it is now evident that both nigra Lhalamic~1 and nigroslriatal neurones reaive I 'nonosynaptic input from tile su iatum, although thill input probably originates in different paris of the striatum. Tn the earliet study on the str iato-nigro-thalamie pathway, the lesion$ wert placcd in the main body of t!le striawm ll wbereD.$ in the presen t study the lesions were leclted in the ventral st riatum and nucleus accumben$ ,

The orisin of H RP-lo~lItd 00"/011.$ Our resu lts are in ag reement with earlier studiesU,n on HR P in striatonisral

sys tem, demonstratina that the neuron:t l smonth endoplasmic reticulum and the lysosomal s)'$tem con tAin the reaction cnd-product. Two main types of boutoru were found 10 contam reaction end-pro~uct in the substant ia nig ra, fo!low;na injection of HRP ;rHO the nrialum.

T ype I boutons in the present sludy a re identical wi lh type I boutons of Rlnvik and Grofova t ' in the cat, wTth type C boutons;1'I the (atil and wi th endings with large syn.ptie vesicles in the primaleti. It is more difficult 10 cor relate the H.R P· labelled type 2 boutons with any ducribed previously. We may hl.V1: se lected a subpopulalion o r boutons hilherto ul'lrecognized , because we stud ied the synapuc ooll neaiolls o f labelled structures. 1n any caSt there ;$ a dear di fferenu between the twO popu\ations of HRP-Iabelled boutons nOI only in morpho logy but more imponandy in termination. Type 2 boutons were mainly fcund on perikarya and proximal dendrites while type I bouton$ occurred mainly on more distal delld tiu::s and nOI on the peri karya of Ilisrosltiatal neurones. This differenu in te rminat ion illdicates a d ifferenti.1 input onto the va rious re<:ipient parts o f nigro5triatal and othe r nig ral output Ileurones.

The pruenee of a large number of H RP·labelled boutons raises Ihe question : are Ihese boutons the terrnillals of strialonigral neurones? Fo llowing injection of HRP ill to Ihe striatum, labelled boutons could appear in the substallt ;; nigra jn J ways: (r) th rough lllterOl rade [rallspan of HRP from the sIn.tum ; (2) they could be local uon co1\atefl!. ls labelled anterogradely followi llg retrograde labeHin! of Il igrowia tal neurones; and (3) they may represent the an terOgrildely labclled boutons of neurollcs in a third nucleus that Wi!S labelled retrogradely from the Stria tum and which sends loog axon oollatcrals 10 the substan tia ni, ra .

II is likely tbat at leut some of the type I boutons are labelled by the first meehaOlstn. Thus, following placement of lesions in thc accumbeM-ventral striatum reliotl, the degenera ting bOUIOll5 in the nigra have, al an u rly sta &e, the same morphological features as the type I HRP-Iabelled bou tons. In rue cases HRp· labelled boutons or type I themselves showed the early stage of degeneralioll (Fig. 6),

,o<Ilo. ti"l ,1\0, ,1><1 Otlr;"'''' f,om ,~at ""' ... of \11< ...... . '" ",I><".he ""rud 0{ HR' 0V<rIa;>< ..;,~ ,10< ......... f ,.,. J....... ,nd_ by W....: ><od. f , ... IIy. ,lie _001, f. , ...... by local u"" coU", .. " cl odo"uf\ed ...... ,0"",.1 n •• 'o"'·· .. ~ . .. "'"1 .... ilo, III<Ir,>hoIo~ r ... ,., .. '" ,,,,. I HR''''1>d .. 4 ""UlOn, '" ''''' ... b<u. .... n;I" . TIIi< 'u,,,,.,, .... ""'1 ,~., ,_ , ""~IO ••• re cl .... , ... , "'p •. boI, 110 .. ,1><1'" """'Q'" or ,10. mediu,""" n'UfOn .. ",j,~ d<nsdy spln~ doo<ln' .. 'h" .... k",,"""~ "'~JUI to tIo.e n.,..-"

No HR'·lahll',d """'0<1. of 'YP< l .. ,,~ 1000<1 ,bo, 0110 ohOW<d .i .... of do~n ... ""n .nd ... , .. ;, 0<, .... ;, " .... "oito. " is ~"'W(",~,,,,,, <lit, bad ...... ... _'1"""'''' 'o'l" (,. pen"'oya cI~, .. _ ..... 1 ... u, ..... ) ond ..... ,10, .,... .... 'riul """Pl;~ 'p<O>I.ut;OO .. ..,m. Of the """,on, 'bat do","",,1e<1 . ft .. , ... ,,""lnCn,"" • _ '. , ... 0<£00"' .............. "., """g ... AIlI .... p .1>< 0" .... DI '11'" 1 bo.'"", f""" ..... 00 .. lot \11< >Om'"m ' .... , ... <oo~,",.tion by "' ... d>r"'" ,.,..hod •• i' " ",ni~ .... ' ,"-, !.h .... I •• ""'''I'!!"'''''' .}'S, .... ,Iw Cl", be labd'''' by HR? inJOC'<d mto !he ..... , .... and wIolCll ... "' .. " .. on \11< pa;wya . 0<1 ",,,,i",, <1< .... " , .. '"

.'FO«"'''' ...... On ... I'~ "'''</'''_ ,..,. """""_I,, ...

'0 o, ~" '0 u<>de,,,. rwI '.0 f."ollo",,1 ,oIe cl (10< "",oooy<.p'ic p . ....... ~ from ...... o-u I. ,lie """, .. _.,,01 .. " ..... 10 ni ........... ' ..... ' ...... _ ..... '0 1<I •• " fy ,~. "' ..... ran ... it"" ",. both ,~o . !!".«., I<,ml ... I, •• d ,lie '«'PI,n' .IV""';.'" ..... ""' .. "1"'0"", ,h<nt is. .. P ...... ~ no d lreel ._ .... coo d ...... so- ..... u .. ~ f.- ~ .. <><hemotol .rod J><UIO<JI."' ..... ".d, ... n. 'lri"'~"'I'" '"~"."GO , co.,"""", p,ojc:o,;"" 0" ....... "'''"'1 from ,he '"'''-;0' It';.,,,,,, ,. ,he ,.,u.l<.lI odd ,10< co..w """" ... _.," __ oI''''''D., "';0. (s-n of ,10< ., .. alr«UIII by ............ ,) 'ON' ••• "'''''._ P ;",mU'Dru'"'' un bOdie,lI. S.l»t •• « p ",,,,'"notuc",", ~b«, con be: lUG to~ ........ '" olId .... It.t '0 • ..,... compKI' ..... 'c .... f ... """. "~tul""' .. oIly ...... ,0;." """,.n ••• , .... , ""1 (P. So",osP. I. I'1-''''''Y. " . C. Cudt o. A. D. S .. "" .nd J P Oolam •• np . bH.~", ............ ' iOOl.). H.,.."",.;.." ..... "bIo "'," n;,rol •• bwt_ 'd_ "'" 0ri.,Ji ..... f,,,.. ........... I. ,~, .... ",,' ....... 1 " lOO' btU ... '''' ....... no rk<,,_ ... ,he ''''OWl' of .ub"'.« P in ,be .ubl:o.tio nip. lollowm, .... iOll \. ,he rlD<I<~ ...... , ....... " . ,W_aJI -..-<>61 ....... 011 of .... di" ..... _ cl \11< ........ n'" .......... "'" pe,fo''''~. The ,"'po, ...... of 'ub<li.i~ in, ,o. ni, ... ..... ,hown by W., . .. . nd F ..... .... "'"". 10.rwI • Ideal .. _ .. '0 ,.,. 1<",,1 o! ~~ ...... " 6eeo,burlol<

"'.""1 '0 ..... 001 ....... "'01 wbstontia nil" (,ndvd,ol put '" 1'" PO" <OnIpKI.) follo""n, p'o.c<"...,' of ..... " . i. ,t .• "_0. a<:cItml><n'. Th • •• ,lie , vi ....... .. rtf .... , f . ....... y-a"';".b"'rr' " ... u ....... , ...... ll1e ................ , """"'" f,_ ,ht: ""","be .. '0 ,he n'I".

The m'jori,y of .i"O$hWo I "".'on« or. do"", .. i. ettiC. ............ ha .. \IUJl f ........ ".lKI< ')·' ....... h~"" ... _ .. «dopa .......... 1'_ ...... tI._ .. cI .... ,lie

..... ;bi'''y "' .. iOrt>e .W."",, /'""' ,he ",.".1 "n .... 1 ' <5'0' I<, .. in_ on oon·

. """""PO ... " ... , ...... 1 M.ronu. IIoc It"" .... du.. d<Fn<' .... 1 bow ..... etln

, ... tltl, b< (.ood o ...... of ,1Ie .... "'V. ""ly '.b<11<d """' ........ lien ,hey ., ..... 1 ... o.

'" .... '" ... ,.,.....,_ ~ ,Iuo, 'h< o!npoMi.>o,1'< ,,~,,"" .... , ...... " .... "'-" •

mon .. y",,,,;" lOP"' (."'" tOo: .""."'totn.·...,' ... ' "';" .... 1'..",,,,,, f"""",,,~1 Imp/I'M"""

Tt..."' ... ", 10 b< f"~,~OtI.'ly d ... ,,,,,..u. "'Mhu..bt ...... ,ri."' ............ ... "'" /bod,..,._ ,lie input of "'I'''''n'''' """'0 .... "'Y ha"" 1.""""",1 ,,"p'oa_ ,,,"' •. The d<s<n<ro'm, 1><>"_, "'. (,, ',nd In .<>n .... "'ith oi""w;,,'" ""1'(1,,<1 .,." "''''',l< r. .... d,ff., .... p.o" of <k ... OAIo", (,he _"., ...... , ,odod; .... ,toe: "",.",be",} f.om ,he I'''' mO)O.hy 01 ,"" IIR~·I.bell«l bou ,o n, b<uu .. ,h. ,,, .. , ","'y '""" y .Itow<d .1,., oI4<:cOl<IO"OO h;, ~kol, ,bot "' .. , or n •• HRP·LoIldIocl ..... , .... ""1' ... «1 (,_ ... u ........ In ........ bodyol", "ri"o .. , h "ftQ .... ""hy oh ...... oo...",d "'.'OfF ncot of II II.P·,.bd locl bo.,,,,,, and d .... or. tinl bc.,,,,,, on .h< ...... nIp""';"" .... ,_ I. i" ,Ious., ........... bI< ,ho • • ", ... , otr • .u.n If ..... ...... orCM, ... h"~ 11"<>"'" d,ff .... , Inlo"u" .... con ..... "" to ""slC ni ,ra' .... ,on., .. ~h i . tU'n p<,,;.cl 11'1. poau._y 011 .... 1<1 ........ co.,,~, .. ~ OOI'Y" • .;",,,,,. ( .. _01>1><) '''':lbI<~ ''''''11 " 0",, " 'ovol .... r<1'O~' of 'k' """'""' "''' ><11 f .. d b.od:.n 10 ni"", ""., ............. PfOf«t ' o.d;lfcr<,,''''''' of tho a ....... Tloi. ,<01,,1 ."i"",". ""CO ,,,,, ''''0-IBIi"1 I.bd.,d ni" ... ";,,al ... ,.,....111 .. ,...,.,"«1 <1< ..... "., ......... """Id ..." 'aoc oak ... ~P HttPfromtho Olea otIe< .. ~ 'of d,. 1<0;0" bc<:>~" " .. " ........ ""Id ., .. ~."",ro .. ""Uo<oo, ... tion. h '. '''0 .""ko'""" ''''''' ,."o¥<oj ... ""lIi", o«~,,<d .. a a>.O. c.aI .. , .... k, .. _ ''''' ._a of. ... ,05Iri ... , ccI4 do _ bra..clo 10 "'t< ..... of. tho "ri".", •• ,,..,"' ...... by , .... ,,,k 01 d",,~1e lo".led ull' '"

uJ"rim'"U i"y", .. ". oh< u" 01" ~"OI'<>«n' d)'<.l" We l<.uh,..jy COII<Iud< , ......... bd'"1 of HRP·labelkd t>o<>IO,," I. ",.'oa

...;'" "'I ..... " ... ' ... U' ....... «>n~'1C" .. i,h , pejnN.,.poin, (i. '''Ho-atU) ,,0;.

I>IO<I'J ", .. 01",., ,lit N .. ,I "''*'''00<1 '" ,"" ... ;, _1 o(,1It ...... 'u"' ...... 'ha! ,lie .in." i ......... ''''' ...... Wl 0«""'''' ....... 1<01 .. , .. ,.'" •• ,_ .. """ .. d..,.; .... I, y, ,.". ,col ;" ,I';, "" .. Jo ,.;,"'" ""'" ' 0"" f.,,", ,hi> 'ea''' ' ".;" "'0"00, • .,.,,,, """ .. .. .. ,lit .;"-'1 ................ , ",-, <k<-ooh<r< ,. ,It.< .. " ........ n.. I"." <0<><1 ... , .. is .. o.;r«""" w,," ,"" ,n, •• prt. .... "", of N,.," " .1 ".

T'" ..... ".l IIn.w ....... do ••• __ .. ...,.. ;,. kfto ..... 10 .-.... li'Oboe _ .... if"" ,ri." .. "" '" N .... • rut 00_", O"'fl>M.1 .nd ~.p!a"'"; Mo •• "",,, .1 "'). 00 ,h. 0,1\" lu.oi •• h. ",ai. _, of , ... "'lid"""'"""" ........ ",OIl 0( ,he HR' .... ",,.,,«1 pon""PlI<> loo oo_LO-""""" f~t><I_,,, ne "","",y .. ",oe ......... lion th",ugh.he .ubl".'" "'I" d .... "." .. 1«l i. ,~. pt .... ,

,,~j1 be,,,,,,,,,. 'l><'" ''''~ "<At Ill •• ",<>">do. • ",.",.ot bo .... AI 'l>< .,..."'" k,-oI. I"" Oft ·i ... , f",,· bot_. 1;"1>0<."" _ ... JII .... '", ..

Tl>< •• "'on or. ,.at,ful '0 M,., "ta •• $lire" for her sl.,Ufl>lI«M><aI_ ..... . •• d P~"'''''''P~'''_~ 'ON .... dy_,,,,_«d by.,..,u f.o"" , ... W.lkome T .... . Ih. 11.0)'0.1 Soci<ly 'n~ ,he e. P. A"'-.I ..... Ct~h.lo"""i" T, "".

263

H Nein, D . 9. , Puoy, L A. and Gold, M. S., Identificahon of 11 subrcJiol'l wilhin 1'11' neostriatum (or the dopamtneta1c modulation fo talent hypolhalalNC: sdf-1Iimutllion, arDlIl Rurtlr,.II. 151 (1971) SIS-S29.

26 Powell, E. W. and leman, R. B .• Conncc:li(lns of the nucJcl.l' Ittumbens, Brmll Rtum'(h, 10S (1976) 389-40)

27 Reynolds , E. S" The use of ltad Cllralt at hiah pH as an eloctron opaque slain In electron microscopy, J. C,/J B/~I .• 17 (1961) 103-2.12.

21 Rin .. ik , E. and Crotoyj, I .. Observatlonl on It\/: line SlNC1UI'( of lhc. JUNta m;. nl,ra of the (aI, Exp. Bm;" Ats., I 1 ( 1910) 2Z9- 1-41.

29 Schwyn, R. C. and Fo". C. A., The p!ulUle substantIa ni,r. : A Ciolci and electron micrrucoPic sludy. J. HinifMx/o",", Ij (1974) 9}-lll.

]0 SomocYi, P .. Bol.lm. J. P. and SI\\ilh, A. D., Monosynaptic: con ica l illpul "1(1 local axon c:ollatc: ... h of identified Itrlllonlnal ncuronl. A l!.ht and e!CClron mocroscopH; sTudy usins the GoJ;j·pcroxidast tra.niport·deaenef1ltion procedure. J. c()mp. "'t!III'Of" in presto

) . Somogyl, P., Hodpon, A. J. and Smith, A.. D., An approach 10 "acin, neuron new.orks in the o: rel)(l l COrtex Ind baSIl pnglia. Conlbinal;on or Ool,i'SIl;",n" retr~dt transporl or horu-/'IId;s" peroxidase and anterograde deaencntion ol '~nlptic: boutons in the same. material , Ntum. 1Litllr~," (1919) ISOS- ISH

Jl SOlTlOl)'i, P. and Smith. A. D .• PrOject ion of neosl(itlal spllly neurons 10 IIIe Subst&IIUI nigra. Application or a eonlbined Golgi·sul lnin, and horseradish peroxid-ase lransport procedure at both !i,hl aod eleet roll microscopic levels, Brn;" Rt!unrtll, 178 (1979) 3-15.

J) 5olelo, C. and RldIe, D., The smooth endoplasmic reticulum .. nd IM relrOlrade and (asl orthcIUM transpon or horserudish pero~jda!oC in the niGrc>sldllc-nigr"loop. A",,, . £mOr}'o/ .. 146 (I974) lOO-l it.

}-'I Swansoti. L W. and COWln. W. M .• A nole on (he coonections and dewJopment of the nuc:leus .ccumbt.ns. B"n;" Rt!lt!n, rh. 91 ( 1975) 324-)30.

34 SUbo. J .. Orpninlion or,he as.cenc!inlstriatll J.lfelents in monkeys, J . Nlmp Nt!ltrol., 189 (1940) )07- 123.

)6 Van der Kooy. D" The orsanimlion o( Ihe thal. mk, nilUI .nd r.phe edls pro,J«:tin, 10 tt10e medu! lIS laletll caudale-pulJ.men in rat . A nuore5Ctrn doubk;O\.bdhroa study. /kn;., Ru."rt/l, 169 (1919) )11 -)31.

) 7 V,,.. del Koo~ , D. I nd Wis.e, R. A., Rel(ogrlde nuoresc::cnl lrad rol ot SUbsun111. niar. neurons combined ... -idl alcc~minc hi"onuoresc:elKe, 8rD/" Rt_cl,. 18) ( 19SO) 441"'~).

J8 Wa.lu~ I . • 1Id Fo ronum, E. BioehctNeal tyideno:t (or Y-lImjllObul~ralc corotaininl fibrcs rrom the nucleus .cx:umbcM 10 Ihe. sutnu nlia roilra Ind ve:nlrJ.llegrnenlll l un in Ihe: ral. Ntllr()lrlmu. S (19SO) 6)-1l.

i · 246 sometimes also received degenerating boutons originating from neurones in the nucleus...

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