Antidiuresis of Centrally Administered Amines and Peptides and Release of Antidiuretic Hormone from Isolated Rat Neurohypophysis

Abstract

Effects of biogenic amines and peptides on urine outflow and ADH release were studied using intracerebroventricular (i.c.v.) perfusion experiments and isolated neurohypophysis incubation studies. Decrease in the urine outflow was observed after norepinephrine, histamine and angiotensin II had been administered i.c.v.. The effect of norepinephrine was prevented by phentolamine. Phentolamine alone also acted as an antidiuretic. α-Adrenergic and histaminergic mechanisms may thus involved in ADH releasing system and this system might be also responsive to angiotensin II. When the isolated neurohypophysis was incubated in the presence of norepinephrine, histamine, angiotensin II amide 5-valine or bradykinin, release of ADH was increased, and the effects of norepinephrine and histamine were prevented by phentolamine and promethazine, respectively. Phentolamine but not promethazine alone increased ADH release. On the other hand, serotonin, dopamine and angiotensin II 5-isoleucine did not result in an ADH release from the isolated neural lobes. Our findings suggest that when the local concentration of norepinephrine, histamine or peptides is increased to the extent where the posterior lobe of the pituitary is stimulated directly, the ADH release is enhanced.