Grafts of embryonic substantia nigra reinnervating the ventrolateral striatum ameliorate sensorimotor impairments and akinesia in rats with 6-OHDA lesions of the nigrostriatal pathway.

Previous studies have shown that transplants of embryonic substantia nigra, which reinnervate the dorsal neostriatum, can compensate for certain, but not all, behavioural deficits induced by unilateral or bilateral destruction of the nigrostriatal dopamine pathways in adult rats. The present study shows the nigral transplants which are placed in the lateral cortex so as to reinnervate ventral and lateral parts of the neostriatum, give an entirely different pattern of behavioural recovery. Thus, the laterally placed grafts were more efficient than the previous dorsally placed ones in compensating for the sensorimotor asymmetry in unilaterally lesioned animals, and the akinesia seen after bilateral lesions. Conversely, the drug-induced motor asymmetry which was completely abolished by the dorsal grafts was not significantly affected in the present animals. These results support the idea of topographic heterogeneity with respect to striatal functions, and suggest that the technique can be used as a tool for more detailed analysis of the functional organization of the meso-telencephalic dopamine systems and the functional heterogeneity of the dopaminergically innervated striatal-based forebrain regions.