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Losartan, a nonpeptide angiotensin II receptor antagonist, was used to establish the role of brain AT1 angiotensin II receptor subtype on the natriuretic, antidiuretic, and dipsogenic actions of centrally administered renin. Intracerebroventricular administration of renin reduces urine volume and increases sodium excretion and water intake in conscious, male, hydrated rats. Losartan (3 or 10 mg/kg, sc) reduced the increased sodium excretion and totally inhibited the antidiuretic action induced by intracerebroventricular renin. When both renin and Losartan were given intracerebroventricularly, at the highest dose, there was a potent inhibition of the antidiuretic and natriuretic actions. Peripheral and central administration of the AT1 receptor blocker significantly lengthened the onset of drinking behavior and reduced the cumulative water intake observed after intracerebroventricular injection of renin. Our results strongly suggest that the brain AT1 receptor subtype mediates the physiologic actions of angiotensin II, such as drinking behavior, the increase in sodium excretion, and vasopressin release.

Intracerebroventricular (i.c.v.) administration of JA116a, induces an increase in urinary volume and sodium excretion in conscious male hydrated rats. The involvement of brain dopaminergic neurons in the JA116a renal action was investigated. Diuretic and natriuretic action of JA116a was blocked by haloperidol pretreatment. The renal effect was prevented by selective dopaminergic neuron, denervation by i.c.v. administration of 6-hydroxydopamine in combination with desmethylimipramine. Our results suggest that JA116a acts centrally, at least in part, via an interaction with endogenous dopamine neurons.

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