CHANGES IN ALPHA(1)-ADRENERGIC NEUROTRANSMISSION ALTER THE NUMBER OF SOMATOSTATIN RECEPTORS IN THE RAT HIPPOCAMPUS

The administration of an i.p. dose of phenylephrine (2 mg/kg) increase d the number of [I-125]Tyr(11)-somatostatin ([I-125]Tyr(11)-SS) recept ors and decreased their apparent affinity in rat hippocampal membranes 7 h after its injection. Prazosin (20 mg/kg, i.p.) administered 1 h b efore phenylephrine reversed effects of the latter on SS binding. Praz osin alone decreased the number of SS receptors without changing the a ffinity. The addition of phenylephrine or prazosin (10(-5) M) to the i ncubation medium did not change the SS binding characteristics. The pr esent results support the notion that the alpha(1)-adrenergic system r egulates the binding of SS to its specific receptors in rat hippocampu s.