A COMPARISON OF THE BEHAVIORAL-EFFECTS OF EMBRYONIC NIGRAL GRAFTS IN THE CAUDATE-NUCLEUS AND IN THE PUTAMEN OF MARMOSETS WITH UNILATERAL 6-OHDA LESIONS

The behaviour of marmosets with unilateral 6-hydroxydopamine lesions o f the nigrostriatal bundle and grafts of embryonic mesencephalon in ei ther the caudate nucleus or the putamen was compared with that of lesi on-alone and unoperated controls. The grafts comprised injections of c ell suspensions prepared from marmoset Ventral mesencephalon (i.e. all ografts) targeted at four sites either entirely within the caudate nuc leus or entirely within the putamen. Behavioural tests, including meas ures of amphetamine-induced rotation, neglect and use of each arm to r etrieve food from inside tubes, were given before and after the 6-hydr oxydopamine lesion and at regular intervals for 6 months after transpl antation surgery. Grafts in the caudate nucleus reduced the ipsilatera l rotation induced by amphetamine, whereas grafts in the putamen did n ot. Despite the absence of an effect on rotation, the putamen grafts w ere effective in reducing lesion-induced deficits on the task in which the marmosets were required to reach into tubes. In this latter task, the caudate grafts were also effective when the monkeys were given a free choice of which hand to use. However, when constrained to use the hand contralateral to the lesion and graft, the performance of the ma rmosets with caudate grafts was not significantly improved compared wi th that of lesion-alone controls. Neither the grafts in the caudate nu cleus nor the grafts in the putamen abolished the contralateral somato sensory neglect induced by the lesion, although there was a trend for the marmosets with putamen grafts to contact the label on the contrala teral side more quickly than those with caudate grafts or the lesion-a lone controls. These results demonstrate that the location of embryoni c nigral grafts within the primate striatum influences the profile of functional recovery.