Attenuation of angiotensin-induced water intake in estrogen-treated rats.

Chronic treatment with either estradiol benzoate (31 and 57 microgram/kg/day) or ethynyl estradiol (30 and 72 microgram/kg/day) attenuated the drinking responses of female rats to acute administration of either isoproterenol (25 microgram/kg, SC) or synthetic angiotensin II (100 and 200 microgram/kg, IP). While these studies do not rule out the possibility that attenuation of isoproterenol-induced drink in estrogen-treated rats may be associated with a defect in renin release, attention is also apparently associated with a reduced responsiveness to angiotensin II. This may be related to reduced permeability of angiotensin II at the level of the circumventricular organs of the brain; to hyporesponsiveness of receptors for angiotensin II mediating thirst in the central nervous system, or to mechanism beyond the receptor that are responsible for the conscious behavioral changes which normally accompany angiotensin II-induced thirst.