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

Departamento de Fisiologia, Faculdade de Medicina de Ribeirao Preto, Universidade de Sao Paulo, SP, Brasil.

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.