Vasopressin and blood pressure regulation.

The vasoconstrictor actions of arginine vasopressin (AVP) have been shown to occur in concentrations much lower than previously thought. Pressor responses to AVP are a poor index of vasoconstrictor activity since, in contrast to other vasoconstrictor agents, the expected rise of pressure is offset by dose-dependent decreases of cardiac output. The mechanisms for this appear to be, in large part, modulation of the autonomic nervous system whereby AVP enhances vagal nerve activity and reduces peripheral sympathetic nerve activity. AVP enhancement of baroreceptor reflex gain is in part responsible for these changes in some species (dog and rabbit), but not in others (rat). The release of AVP appears to contribute significantly to the normalization of arterial pressure in volume-depleted and hypotensive states. The link between plasma AVP and hypertension remains unclear, but it appears likely that it has an important permissive action in the development of sodium-dependent forms of hypertension.