Autoradiographic localization of neuroleptic and dopamine receptors in the caudate-putamen and substantia nigra: effects of lesions.

The localization of neuroleptic receptors was studied in the caudate-putamen (CP) and the zona compacta of the substantia nigra using light microscopic autoradiography of 3H-spiperone binding sites. Lesion of the dopaminergic input to the caudate-putamen produced an increase in receptors in the CP, possibly reflecting denervation supersensitivity. Kainic acid lesions and decortication produced significant decreases of 61% and 18% in striatal receptors. This suggests that in the caudate-putamen most of the dopamine receptors are on intrastriatal neurons, but some are also localized to the afferents from the cortex. Lesion of the nigro-striatal dopaminergic pathway produced a large (48%) decrease in receptor sites in the substantia nigra zona compacta while kainic acid intrastrially and striato-nigral pathway lesions had no significant effect. These results suggest that the majority of dopamine receptors in the zona compacta which bind neuroleptics are located on cell bodies and processes of dopaminergic neurons and are anatomically distinct from dopamine-stimulated adenylate cyclase sites.