Influence of methyldopa and bromocriptine on negative pressure breathing-induced diuresis

The effects of methyldopa, a central alpha 2-agonist, and bromocriptine, a dopaminergic drug, on negative pressure breathing-induced diuresis were studied in the dog. Methyldopa (20 mg/kg i.v. during 20 min) or bromocriptine (0.3 mg/kg i.v.) suppressed the diuretic reflex without changing blood pressure. Since negative pressure breathing-induced diuresis is mainly due to an inhibition of vasopressin secretion, it is suggested that central alpha 2-adrenoceptors and dopaminergic receptors play an inhibitory role in mediating vasopressin release to non osmotic stimuli.