FUNDUS STRIATI VASOPRESSIN RECEPTORS IN BLOOD-PRESSURE CONTROL

Vasopressin (VP), given intracerebrally to rats, can induce antipyresi s, motor disturbances, and increases in arterial blood pressure. The p ossibility that the VP-binding sites in the fundus striati (FStr) coul d participate in these effects was investigated. After a bilateral inj ection of 100 pmol of VP into the FStr, the fever induced by an inject ion of the lipopolysaccharide of Escherichia coli (50 mu g/kg ip) was not affected. Bilateral injections of 100 pmol of VP did not induce mo tor disturbances or alterations in body temperature after either of tw o successive injections. In contrast, bilateral injections of VP into urethan-anesthetized rats induced dose-dependent increases in arterial pressure without affecting heart rate. This increase was blocked by a V-1 antagonist; oxytocin and a V-2 agonist were ineffective. In keepi ng with this preliminary pharmacological analysis, radioligand-binding studies of the FStr revealed binding sites in the FStr exhibiting a b inding profile typical of the V-1 subtype. This study suggests that th e V-1 receptors in the FStr could participate in the central regulatio n of the blood pressure.