Effect of AVP on pressor responses to peripheral sympathetic stimulation in the rat

Studies were carried out to determine whether arginine vasopressin (AVP) could modulate pressor responses to peripheral sympathetic stimulation or potentiate systemic norepinephrine (NE) vasoconstrictor effects. The effects of graded 30-min infusions of AVP (0.02, 0.2, and 2.0 ng·kg^-1·min^-1) on the pressor responses to either electrical stimulation of spinal sympathetic outflow or NE injection (0.1, 0.5, and 1.0 μg/kg) were determined in central nervous system-ablated rats. Spinal stimulation with increasing frequency (0.25, 0.5, and 1.0 Hz, n = 8) at a constant voltage (20 V) or increasing voltage (8, 10, 15, and 20 V, n = 6) at a constant frequency (1 Hz) elicited significant stimulus-response relationships in mean arterial pressure (MAP). Similarly, NE increased MAP in a dose-related manner. AVP had no significant effect (P < 0.05) on pressor responses to increasing frequency or voltage stimulation or to NE injection. We conclude that pressor responses to sympathetic stimulation in the rat are not modulated by actions of AVP to inhibit peripheral sympathetic ganglionic transmission or potentiate NE vasoconstrictor effects.