Fetal substantia nigra and adrenal medullary grafts placed contralateral to the nigrostriatal lesion side induce a decrease in turning behavior but not in dopamine receptor density.

Motor asymmetries as well as changes in the density of postsynaptic dopamine receptors produced by unilateral denervation of the striatum have been reduced by both substantia nigra (SN) and adrenal medullary (AM) grafts. Since to this date all studies have placed the grafts on the side ipsilateral to the lesion, the purpose of this study was to determine whether similar effects can be obtained when grafts are placed contralateral to the denervated side. The results of this study showed that 6-hydroxydopamine-lesioned rats followed up to 150 days with contralaterally placed intraventricular fetal substantia nigra grafts and fetal adrenal medulla grafts have a reduction of turning behavior of 41% and 34% respectively. However, contrary to ipsilateral grafts no normalization of dopamine receptor density as measured by [3H]spiperone autoradiography was observed 6 months after SN grafts, however, after AM grafts normalization did occur except in the anterior portion of the striatum. These results suggest that the compensatory motor changes induced by the grafted tissues could be mediated by mechanisms unrelated to changes in receptor density.