Inhibition of centrally-evoked pressor responses by neurohypophyseal peptides and their fragments

Abstract

Intracerebroventricular administration of fragments of [arginine8]-vasopressin (AVP) such as AVP1–6 and AVP7–9 attenuated the pressor response evoked by electrical stimulation of the mesencephalic reticular formation in urethane-anaesthetized rats. Oxytocin (OXT) and the fragment OXT7–9 were also active, although OXT1–6 did not affect the pressor response. These peptides did not influence the bradycardia accompanying the rise in blood pressure, nor the basal blood pressure. The inhibition of the pressor response was shown for OXT7–9 to be dose-dependent up to 25 ng. These data suggest that oxytocin, vasopressin and some neuropeptide fragments have an inhibitory role in the regulation of blood pressure. Both the covalent pressinoic ring structure and the C-terminal linear portion of vasopressin contain active sites, while the activity of oxytocin appears to be present in the C-terminal tripeptide Pro-Leu-Gly.