Effect of forebrain commissurotomy on recovery from unilateral 6-OHDA lesions of the substantia nigra and circling induced by apomorphine

Behavtoural Bram Research, 17 (1985) 245-249

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Elsewer BBR 00481

Short Communications Effect of forebrain commissurotomy on recovery from unilateral 6-OHDA lesions of the substantia nigra and circling induced by apomorphine HEINZ STEINER, SARAH MORGAN and JOSEPH P HUSTON

Institute of Psychology III, Umverstty of Dusseldo~ Untversttatsstrasse 1, D-4000 Dusseldorf (F R G ) (Recewed Aprd 10th, 1985) (Revised version recewed July 21st, 1985) (Accepted July 25th, 1985)

Key words crossed mgrostrmtal projection - forebram commlssurotomy - recovery of function - 6-hydroxydopamlne turning - rat

We studted the influence of transection of the mterhemlsphenc fiber systems between the anterior and posterior comm~ssures on recovery from turning behawor induced by a unilateral substantla mgra lesion m rats It has been argued that the crossed mgrostrlatal projection ~s revolved m th~s recovery, and its site of crossing has been suggested to he w~thm the region spht Ammals which received this transection &d not &ffer from controls with respect to time-course and extent of recovery from les~on-mduced asymmetries within the 7 postleslon days examined Addmonally, the comm~ssurotomy &d not prevent apomorphme-mduced contraverswe circling

Whereas the homolateral nxgrostrlatal pathway has been well characterized over the last two decades, the sparse mterhermsphenc projecUon from the substanUa mgra (SN) to the neostrlatum has been investigated only recently2"1°,12,13 Evidence exists for a temporal correspondence between the recovery from spontaneous motor asymmetries (turning) reduced by umlateral lesions to the nervous system and an apparent mcrease m crossed mgrothalanuc and nlgrostnatal projections4 After behavioral recovery the structures presumably deafferented by the lesion appeared to recewe an enhanced input from the contralateral SN A causal relatlonsinp between these two phenomena was suggested by the observation that prevenUon of lesion-induced turning

suppressed both the neural alterations and the behavaoral recovery8 If changes in the crossed efferents of the SN are essential for recovery from lesion-reduced asymmetries, then their destruction should influence the recovery However, the route by winch these fibers travel to the contralateral strlatum is stall unknown A recent study suggested two sites m the &encephalon as main 1ocl of crossmg of lnterhemlsphenc strlatal fiber connections, one m the massa mtermedla of the thalamus (thalamlc comrmssure), and the other dorsal to the third ventricle at the level of the anterior hypothalamus 12 Thus, the present experiment was undertaken to study the mfluence of a imd-saglttal transection of the mterhemlsphenc fiber systems

Correspondence J P Huston, InsUtute of Psychology III, Umverslty of Dtlsseldorf, Umverslt~itsstrasse 1, D-4000 Dusseldorf, FRG 0166-4328/85/$03 30 © 1985 Elsevier Science Pubhshers B V (Biomedical Dwmlon)

246 of the forebraln on recovery from spontaneous motor asymmetries induced by a unilateral SN lesion Male Wlstar rats (185 _+ 30g body weight) were kept in group cages with food and water freely available They were randomly divided into two groups (split brain and control) Under Equlthesin (3 ml/kg) anesthesia the animal's head was mounted in a Kopf stereotaxic frame (Incisor bar 2 5 mm below the mteraural hne) The split brain animals received the mld-saglttal commlssurotomy using the following procedure To allow access to the mldhne tissue, a bone flap (6 mm × 11 mm) was removed, and the superior saglttal sinus was retracted to the right side 16 A 5 mm-wlde blade was then lowered saglttally between the two hemispheres until it touched the base of the skull The rostral edge of the blade was 8 5 mm rostral to the interaural line To diminish bleeding a RF current (60 mA, 450 kHz, 10 s, Erbotom T175D, Erbe, Ttiblngen) was delivered to the blade The rat was lying on a metallic blanket which served as the indifferent electrode This treatment resulted In coagulation of surrounding tissue and broken blood vessels Eleven days later a unilateral neurotoxlc lesion was made in the animals of both groups by the infusion of 6-hydroxydopamlne (6-OHDA hydrochloride, Sigma, 4 #g dissolved in 2 #l of saline containing 0 2/~g/#l ascorbic acid, speed of infusion 0 4/d/mIn) into the area of the rostral border of the SN The coordinates used were (in mm) A, + 4 0, V, + 2 0, L, 1 5, and these corresponded to KOnIg and Kllppel 5 coordinates A, 2970, V, - 2 2, L, 1 6 The infusion cannula was withdrawn 5 min after the end of the infusion Behavioral testing was carried out in 5-min periods 1 day before (POD - 1) and 1 and 7 days after (POD + 1 and P O D + 7, respectively) the 6 - O H D A infusion It was performed under red light between 17 00 and 19 00 h in the test box (60 cm × 80 cm) To encourage exploratory activity this box contained several junk objects Its floor was divided into 12 squares (20 cm × 20 cm) to allow the measurement of locomotor activity and the diameter of the rotations During 5-mln testing periods motor asymmetry was measured by counting lpslverslve

and contraverslve rotations, which were defined as body turns of at least 270 ° and not more than about 20 cm in diameter Locomotor activity was analyzed in terms of the number of lines crossed by all 4 paws (crossings) Animals which fmled to show crossings because of poor physical state were dropped from the experiment Between 13 and 15 days after the SN lesion, the split brain animals were additionally tested for apomorphlne-lnduced turning They were put in rotometers 9 and the number of full turns was recorded for 60 mln after the administration of apomorphine (apomorphlne hydrochlorlde, m saline, 1 0 mg/kg, s c , Woelm Pharma) After behavioral testing the rats were perfused through the heart with 10~o formalin in buffered saline containing 5 ~ sucrose Their brains were cut in 50 #m frontal sections, mounted, and the cell bodies were stained with neutral red The extent of the sag~ttal transection was reconstructed, and the degree of the loss of neurons within the SN pars compacta was estimated The transection split the mldhne nuclei and the interhemisphenc fibers between levels A 7 5 and A 2 85 (Fig 1) The followang crossmg fiber systems were completely interrupted anterior commissure, fornlx, ventral hippocampal commissure, and thalamlC commissure There was some variation m the destruction of the optic chlasm and the supraoptIc decussatlon The optic chlasm was completely transected in most animals, whereas the supraoptic decussatlon suffered minor damage only in the rostral part in most animals The corpus callosum, the dorsal hlppocampal commissure, and some rostral parts of the supramammlllary decussatlon were partially spht Inspection of the SN pars compacta revealed an almost complete loss of neurons ipsllateral to the infusion of the neurotoxln in all animals Statistical analysis was performed on the behavioral data of 11 spht brain and 15 control rats Differences between the two groups were tested with Mann-Whitney U-tests14 Intragroup comparisons were performed with Wllcoxon tests ~4 Exact P-values are presented for 2-tailed comparisons Fig 2 shows the mean number of ipsiversive rotations (Fig 2 A) and the mean

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Fig 1 Schemanc sagittal wew of the bram as seen from the m~dllne showing the mterhemlsphenc fiber systems transected by the commlssurotomy AC, anterior commissure, CC, corpus callosum, CIC, inferior colhcular commissure, CSC, superior colhcular commissure, DHC, dorsal hlppocampal commissure, DTGX, dorsal tegrnental decussatlon, F, fornlx, OX, optic chmsm, PC, posterior commissure, SOX, supraopnc decussanon, SUMX, supramammlllary decussatlon, TC, thalamlc commissure, VHC, ventral hlppocampal commissure, VTGX, ventral tegmental decussatlon, XSCP, decussatmn of superior cerebellar peduncle, 3V, third ventricle

number of crossings (Fig 2 B) measured during the 5-mm exploration periods Whereas the animals did not turn m either dlreclaon before infusion of 6 - O H D A into the SN, afterwards all rats rotated exclusively towards the side of the infusion On P O D 1 the spontaneous lpswerslve turning of both groups was Sunllar (P = 0 254) The control group showed less turning on P O D 7 compared to P O D 1 (P = 0 015), thus exhibiting a recovery of funclaon, as predmted Unexpectedly, the rate of turning of the spht brain animals also dropped dunng this tune span (P = 0 026) A comparison of the rates of turning on P O D 7 revealed no difference between the two groups (P = 0719) The slopes of the two recovery curves were also smaflar (P = 0 222, U-test) Thus, both groups can be considered to have recovered from the 6 - O H D A leslon-mduced turnlng to a comparable extent and with a slmdar tune-course. However, recovery from ~pslverslve turning was not complete after the 7-day period m either group, since both groups slall exhibited more turning on P O D 7 than before the 6 - O H D A mfuslon (P = 0 002, control group, P = 0 012,

spht brmn group) The mean number of crossings of the control group was higher than that of the spilt brain group on P O D 1 (P = 0 017) as well as on P O D 7 (P = 0 036) There was an increase m locomotor aclavlty m both groups from day 1 to day 7 after the SN lesion (P = 0 001, control group, P = 0 006, spilt brain group) The increase in actwlty was similar in these groups (P = 0 126) All 9 split brain animals tested for apomorphme-mduced turning exhibited clrchng in the dlreclaon away from the SN 6 - O H D A lesion (P = 0 004, Binomial test), with a range of 103-493 rotalaons emitted dunng the first 60 mln after the lnjeclaon of apomorphme Ipslverslve clrchng was zero or negligible Thus, forebrmn commlssurotomy did not prevent apomorphmeinduced contraverswe turning behavior Fig 3 presents a summary of the behavioral results of the split brain group The results of this experiment show that the transection of most commlssural systems rostral to the SN did not influence motor asymmetries induced by the unilateral destruclaon of the dopammerglc cells of the SN Moreover, the commlssurotomy did not prevent recovery from the lesion-induced turnmg The degree and lamecourse of recovery of the spilt brain group were slmdar to those of the control group However, neither group recovered completely within 7 days Additionally, locomotor actwlty, known to be suppressed after dopamlnerglc cell loss is, increased m both groups during this 7-day period The overall higher level of activity of the control group, in comparison to the spilt brain group, cannot be interpreted, since we did not measure actwlty before the SN lesion Unexpectedly, both measurements indicated recovery of function m the splat brain group which was comparable to that seen m the control group An apparent increase m crossed nlgrostrlatal projections has been found to concur with recovery from motor asymmetries induced by unilateral SN lesions 11 These neural changes were revealed by retrograde tract tracing methods Smce they were detected as soon as 7 days after the lesion, it IS unlikely that they were due to the outgrowth of new collaterals They probably reflected changes in synapnc activity and/or

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Fig 2 A mean ( + S E M ) number of lpswerswe rotations measured during the 5-mm testing period 1 day before, and 1 and 7 days after the undateral infusion o f 6 - O H D A into the substantm mgra (SN) m spht brain and control groups ** P = 0 015, * P = 0 026, Wdcoxon test, two-tmled ~4 B mean ( _+ S E M ) number of crossings during the 5-mln testing period for the two groups Fig 3 S u m m a r y o f the behavioral results o f spht brain group The percentages of the animals which showed turning before and after the infusion o f 6 - O H D A into one substan6a nlgra (SN) are gwen

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synaptlc surface (ternunal sprouting), which led to enhanced uptake and transport of tracer 6 m pre-existing mgrostrlatal connections Transection of such pre-existing fibers should influence recovery subsequent to the SN lesion, ff there is a funcUonal relataonstup between changes m these fiber systems and behavaoral recovery According to the results of the present study the fibers crossing between the anterior commissure and the area rostral to the SN cannot be crucial for behavioral recovery subsequent to a unilateral lesion of the SN Therefore, the question arises as to what extent we mterrupted the crossed nlgrostnatal system The area we spht has been shown to contain most of the mterhemtsphenc stnatal connections ~2, and these could include the cross-

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ed mgrostnatal projection However, a recent study suggested that fibers of tins pathway decussate caudal to the lateral hypothalamus 1 Also, since most SN cells, which gwe rise to the crossed lnnervatlon of the stnatum, are located m the middle and caudal part of the SN 1°, it is possible that these fibers cross in mesencephallc decussatlons Furthermore, the transectlons did not prevent apomorphme-mduced contraverswe turning after a unilateral lesion of the SN. Thus, fibers crossing within this region cannot be crucial for such ctrclmg behavior This result was not unexpected, since there is ewdence that lpsdateral descending pathways medmte circling behavior reduced by apomorphme 3,7 FmaUy, the present expermaent prowdes a new procedure for assessing sensortrnotor deficits reduced by unilateral SN lesions This method was sensitive enough to demonstrate recovery from motor asyrnmetnes within the relatively short period of 7 days Supported by Grant Hu 306/3-2 from the Deutsche Forschungsgemelnschaft H.S was supported by a fellowship from the Deutscher Akademlscher Austausch&enst

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13 1 Altar, A , Neve, K A , Loughhn, S E, Marshall, J F and Fallon, J H , The crossed mesostnatal projection neurochemistry and developmental response to lesion, Brain Res, 279 (1983) 1-8 2 Fass, B and Butcher, L L, Ewdence for a crossed mgrostrmtal pathway in rats, Neuroscl Lett, 22 (1981) 109-113 3 Garcla-Munoz, M , Patmo, P , Wright, A J and Arbuthnott, G W , The anatomical substrate of the turning behawour seen after les~ons m the mgrostrmtal dopamlne system, Neuroscwnce, 8 (1983) 87-95 4 Huston, J P , Morgan, S and Sterner, H , Behaxaoral

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correlates of plastlctty m substantla mgra efferents In B E WIll, P Schmltt and J C Dalrymple-Alford (Eds), Brain Plasttctty, Learnmg and Memory, Plenum Press, New York, 1985 Konlg, J F R and Khppel, R A , The Rat Bram A Stereotaxzc Atlas, R E Kneger, New York, 1963 Knstensson, K , Retrograde transport ofmacromoleeules m axons,Ann Rev Pharmacol Toxlcol, 18 (1978) 97-110 Lelgh, P N , Reavdl, C, Jenner, P and Marsden, C D , Basal ganglia outflow pathways and clrchng behavlour m the rat, J Neural Transm, 58 (1983) 1-41 Morgan, S, Huston, J P and Pntzel, M, Effects of reducing sensory-motor feedback on the appearance of crossed mgro-thalamlc projections and recovery from turning induced by unilateral substantla mgra lesions, Bram Res Bull, 11 (1983)721-727 Morgan, S, Stelner, H and Huston, J P, Relationship between mterhemlsphenc mgrostrmtal projections and the direction of rotational behavior reduced by amphetamine Exp Neurol, 90 (1985) in press Morgan, S, Sterner, H , Rosenkranz, C and Huston, J P , Dmsocmtlon of crossed and uncrossed mgrostnatal projections w~th respect to s~te of ongm m the rat, Neurosctence, in press Pntzel, M , Huston, J P and Sarter, M, Behavaoral and neuronal reorganLZatlon after undateral substantm mgra lesions ewdence for increased lnterhemlsphenc mgrostrmtal projections, Neurosctence, 9 (1983) 879-888 Pntzel, M , Sarter, M , Morgan, S and Huston, J P, lnterhemxsphenc mgrostrlatal projections m the rat b~furcatmg mgral projections and loci of crossing in the dlencephalon, Brain Res Bull, 10 (1983) 385-390 Royce, G J, Cells of origin of subcortlcal afferents to the caudate nucleus a horsera&sh peroxldase study in the cat, Brain Res, 153 (1978) 465-475 Siegel, S, Nonparametrtc Statzstlcs for the Behavioral Sciences, McGraw-Hall, New York, 1956 Wren, P and Robblns, T W , Comparatwe effects of infusions of 6-hydroxydopamlne into nucleus accumbens and anterolateral hypothalamus reduced by 6-hydroxydopamlne on the response to dopamlne agomsts, body weight, locomotor activity and measures of exploration m the rat, Neuropharmacology, 24 (1985) 25-31 Wlrtshafter, D , Asm, K and Kent, E W , Simple techtuque for mldhne stereotaxle surgery in the rat, Physlol Behav, 23 (1979) 409-410

Note added m proof Results similar as presented above have been obtmned by Mmtz, M , Douglas, R, Kellaway, L and van Wagenmgen, G , 'Hemispheric dlsconnecuon and rotational behaxaour', m preparation