1983 Volume 33 Issue 6 Pages 887-894
Conditions for secretion of pressor amounts of vasopressin were sought in conscious, water-replete rats. The characteristic lowering of arterial pressure on injection of a vasopressin antagonist was used to detect vasopressin secretion in pressor amounts. The absence or marked abatement of both baroreceptor impulses and adrenomedullary secretion were found necessary for secretion of vasopressin in pressor amounts : the vasopressin antagonist lowered arterial pressure in rats with sinoaortic denervation and ganglion blockade or adrenalectomy. Besides baroreceptor activity and adrenomedullary secretion, anesthetics were also found inhibitory on vasopressin release in pressor amounts. The adrenomedullary hormone signaling the presence of adrenomedullary activity to the vasopressin releasing mechanism was identified as noradrenaline and not adrenaline. It is suggested that the vasopressin pressor mechanism is recruited to sustain arterial pressure when the sympathoadrenal system fails.