Role of the alpha 1-, and alpha 2- and beta-adrenoceptors of the median preoptic area on the water intake, renal excretion, and arterial pressure induced by ANG II.

The present experiments were conducted to investigate the role of the alpha 1-, alpha 2- and beta-adrenergic receptors of the median preoptic area (MnPO) on the water intake and urinary electrolyte excretion, elicited by central injections of angiotensin II (ANG II). Prazosin (an alpha 1-adrenergic receptor antagonist) and yohimbine (an alpha 2-adrenergic receptor antagonist) antagonized the water ingestion, Na+, K+, and urine excretion induced by ANG II. Administration of propranolol, a beta-adrenergic receptor antagonist increased the Na+, K+, and urine excretion induced by ANG II. Previous treatment with prazosin and yohimbine reduced the pressor responses to ANG II. These results suggest that the adrenergic neurotransmission in the MnPO may actively participate in ANG II-induced dipsogenesis, natriuresis, kaliuresis, diuresis and pressor responses in a process that involves alpha 1-, alpha 2-, and beta-adrenoceptors.