Adrenal-Neurohypophysial Relationships in the Dehydrated Rat

Abstract

The effect of methylprednisolone and desoxycorticosterone (DOC) on pituitary vasopressin content, plasma osmolality and sodium concentration, and urinary excretion of solute and sodium was determined in dehydrated rats. Methylprednisolone administration during dehydration resulted in less pituitary vasopressin depletion, a decrease in plasma osmolality, an increase in urinary solute and sodium excretion, and had no effect on the reaccumulation rate of pituitary vasopressin. DOC did not alter any of these responses. Both methylprednisolone and DOC prevented the dehydration-induced decrease in plasma volume, body water ratio. The mcst likely mechanism by which methylprednisolone inhibits dehydration-induced vasopressin release is by effecting an increased urinary solute and sodium excretion which lessens the osmotic stimulus in the dehydrated animal. The data provide no evidence that the glucocorticoid has a direct central effect on the inhibition of vasopressin release.