Action of AT1 subtype angiotensin II receptors of the medial preoptic area on gonadotropins and prolactin release.
This study determined the effect of the selective angiotensin II (A II) AT1 receptor subtype antagonist losartan in the medial preoptic area (MPOA) of ovariectomized rats, treated with estrogen or untreated, on the release of gonadotropins (LH and FSH) and prolactin (PRL). The MPOA is sensitive to the action of A II and contains cell bodies of neurons producing luteinizing hormone-releasing hormone and a large density of estradiol receptors. Plasma FSH was not altered in any situation. However, losartan blocked and estradiol facilitated the stimulating and inhibitory effects of A II microinjection into the MPOA on LH and PRL secretion, respectively. The results indicate that these effects are mediated by AT1 receptors in the MPOA and that estradiol may modulate them. On the other hand, losartan itself reduced LH secretion in ovariectomized rats, indicating that the increase in the secretion of this hormone, after removal of the negative feedback caused by estradiol, is due, at least in part, to the action of A II on AT1 receptors of the MPOA.
Dornelles
R C
RC
Faculdade de Medicina de Ribeirão Preto, Departamento de Fisiología, Universidade de São Paulo, Brazil.
Franci
C R
CR
D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007700:Kinetics; D019808:Losartan / Q000008:administration & dosage / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D008845:Microinjections; D010052:Ovariectomy; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000502:physiology*
D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D019808:Losartan