Autoradiographic localization of [3H]reserpine binding sites in rat brain.

[3H]Reserpine was administered (i.v.) to rats and they were killed 7 days later. At this time, the regional localization of radioactivity paralleled the distribution of specific binding sites observed in other laboratories. Autoradiographic studies of certain areas displayed a striking localization of radioactivity. There was a marked association of autoradiographic grains with areas containing catecholamine systems. In particular, the locus ceruleus, the caudate-putamen, the nucleus accumbens, the dorsolateral septum and the infundibulum had high grain densities. In the caudateputamen, there was a clear localization of grains to the neuropil. There was also a striking association of autoradiographic grains with certain hypothalamic nuclear, i.e., the dorsal premammillary nucleus, the prelateral mammillary nucleus and the lateral mammillary nucleus. In these areas, the grains were clearly localized in the cytoplasm of the cell bodies. All of the above localizations of autoradiographic grains were blocked by administration of unlabeled reserpine before injection of [3H]reserpine. The significance of these findings and their relationship to the clinical actions of reserpine are discussed.