Effect of vasopressin infusion and sciatic nerve stimulation in isolated dog hindlimb

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Abstract
Measurements of changes in peripheral venous pressure in digital and muscle veins, arterial pressure, leg weight, and venous outflow were made under conditions of constant arterial inflow during vasopressin infusion into the isolated dog hindlimb. Evidence is given to show that vasopressin exerts a constrictor effect on the peripheral veins of the dog and that this constrictor activity is present after adrenergic blockade with phenoxybenzamine and after norepinephrine depletion with reserpine. It is also shown that exogenous levarterenol can cause additional vascular constrictor activity after a maximum pressor response has been obtained with vasopressin, thus demonstrating either separate sites of action for the different hormones or a limiting action to the excitatory activity of vasopressin by the same effector cell. Peripheral vascular refractoriness to subsequent doses of vasopressin can be decreased by sciatic nerve stimulation and the decrease in refractoriness is more pronounced if stimulation is performed after administration of levarterenol.