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) increased the number of [125I]Tyr11-somatostatin ([125I]Tyr11-SS) receptors and decreased their apparent affinity in rat hippocampal membranes 7 h after its injection. Prazosin (20 mg/kg, i.p.) administered 1 h before phenylephrine reversed effects of the latter on SS binding. Prazosin alone decreased the number of SS receptors without changing the affinity. The addition of phenylephrine or prazosin (10(-5) M) to the incubation medium did not change the SS binding characteristics. The present results support the notion that the alpha 1-adrenergic system regulates the binding of SS to its specific receptors in rat hippocampus.