[Role of the hypophysis in the renal responses upon stimulation of the brain osmoreceptor].

The experiments were performed in rats anaesthetized with alpha-chloralose and urethane. Intracerebroventricular administration of hypertonic saline (icv. HS) resulted in an increase in renal plasma flow rate, glomerular filtration rate, urine flow rate, urinary sodium excretion, urinary potassium excretion, and osmolar clearance, and a decrease in free water clearance. These responses were abolished in hypophysectomized rats, but were not significantly affected by intravenous injection of vasopressin (VP) receptor (V1 and V2) antagonist. The urinary dopamine (DA) excretion did not change significantly after icv. HS. Moreover, administration of benserazide, an inhibitor of the enzyme L-aromatic amino acid decarboxylase that converts L-dopa to DA, did not attenuate the diuresis and natriuresis induced by icv. HS. These results suggest that the renal responses upon stimulation of the brain osmoreceptor are dependent on the integrity of the hypophysis, while the VP and DA are not essential to these renal responses. The hypophysial factors responsible for the icv. HS-induced renal responses remain to be explored.