Striatal opiate receptors: Pre- and postsynaptic localization

Autoradiographic localization of opiate receptors in the rat striatum with specifically bound ³H-diprenorphine reveals relatively small, high density clusters of receptors, a high density band of receptors along the striatal-callosal border, and a lower density of receptors spread over the remainder of the neuropil. Placement of kainate lesions resulted in a 94% loss of receptors in the clusters and a smaller loss in other areas. Removal of the dopamine-containing input to the striatum by placement of medial forebrain bundle lesions or by intrastriatal injection of 6-hydroxydopamine resulted in a greater depletion of receptors in the non-cluster areas compared to cluster areas. In repeated biochemical and autoradiographic studies, no change was found after either decortication or placement of thalamic lesions. It is concluded that the bulk of striatal opiate receptors are localized postsynaptically on intrinsic striatal neurons and their processes with the bulk of the remaining receptors localized to the dopamine-containing axons and terminals.