Alpha- but not beta-adrenergic receptors mediate the effect of angiotensin II in the medial preoptic area on gonadotropin and prolactin secretion.

The aim of this work was to study the participation of alpha- and beta-adrenergic receptors on the effect of microinjection of angiotensin II (A II) into the medial preoptic area (MPOA) on the secretion of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) in estrogen-primed ovariectomized (OVX) rats. Microinjection of A II into the MPOA increased plasma LH. This effect was reduced by previous microinjection of an alpha- (phentolamine), but not a beta- (propranolol) adrenergic blocker into the MPOA. Plasma PRL decreased after microinjection of A II into the MPOA, but this effect was unchanged by phentolamine or propranolol. There was no change in plasma FSH in any condition. These results indicate that A II in the MPOA stimulates LH secretion and inhibits PRL secretion in estrogen-primed OVX rats. The effect on secretion of LH, but not of PRL, is mediated by alpha-adrenergic receptors in the MPOA.