Tissue specific regulation of "peripheral-type" benzodiazepine receptor density after chemical sympathectomy

The characteristics of 3H]Ro 5-4864 binding to "peripheral" benzodiazepine receptors (PBR) in the central nervous system and peripheral tissues were examined after chemical sympathectomy with 6-hydroxydopamine (6-OHDA). One week after the intracisternal administration of 6-OHDA, the number of 3H]Ro 5-4864 binding sites (Bmax) in the hypothalamus and striatum increased 41 and 50%, respectively, concurrent with significant reductions in catecholamine content. An increase (34%) in the Bmax of 3H]Ro 5-4864 to cardiac ventricle was observed one week after parenteral 6-OHDA administration. In contrast, the Bmax of 3H]Ro 5-4864 to pineal gland decreased 48% after 6-OHDA induced reduction in norepinephrine content. The Bmax values for 3H]Ro 5-4864 binding to other tissues (including lung, kidney, spleen, cerebral cortex, cerebellum, hippocampus and olfactory bulbs) were unaffected by 6-OHDA administration. The density of pineal, but not cardiac PBR was also reduced after reserpine treatment, an effect reversed by isoproterenol administration. These findings demonstrate that alterations in sympathetic input may regulate the density of PBR in both the central nervous system and periphery in a tissue specific fashion.