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dc.creatorLima, Fernanda Barbosa-
dc.creatorOta, Fábio Honda-
dc.creatorCabral, Fernanda Jankur-
dc.creatorBianco-Borges, Bruno Del-
dc.creatorFranci, Celso Rodrigues-
dc.identifier.citationLIMA, F. B. et al. Estrogen, but not progesterone, induces the activity of nitric oxide synthase within the medial preoptic area in female rats. Brain Research, [Amsterdam], v. 1578, p. 23-29, Aug. 2014.pt_BR
dc.description.abstractThe control of gonadotropin-releasing hormone (GnRH) secretion depends on the action of ovarian steroids and several substances, including nitric oxide (NO). NO in the medial preoptic area (MPOA) stimulates the proestrus surge of luteinizing hormone (LH). We studied the effect of estrogen (Tamoxifen-TMX) and progesterone (RU-486) antagonists on mRNA and protein expression of NO synthase (NOS), the enzyme that produces NO, as well as its activity within MPOA. Female rats received s.c. injections of TMX (3 mg/animal) on first and second days of the estrous cycle (9 am), RU-486 (2 mg/animal) on first, second, (8 am and 5 pm) and third days of the estrous cycle (8 am) or oil (controls) and were killed on the third day (5 pm). Real time-PCR and western blotting were performed to study NOS mRNA and protein expressions. The NOS activity was indirectly assessed by measuring the conversion from [14C]-l-arginine into [14C]-l-citrulline. TMX significantly decreased neuronal NOS (nNOS) mRNA expression (90%), and the activity of NOS, but did not alter nNOS protein expression. Also, TMX significantly decreased LH, FSH, estrogen and progesterone plasma levels. RU-486 nor affected NOS mRNA and protein expressions neither the NOS activity in the MPOA, but reduced FSH levels. The nitrergic system in the MPOA can be stimulated by estrogen whereas TMX decreased NOS activity and mRNA expression. In conclusion, the involvement of the nitrergic system in the MPOA to induce the surge of LH on proestrus depends on the estrogen action to stimulate the mRNA-nNOS expression and the activity of nNOS but it does not seem to depend on progesterone action.pt_BR
dc.sourceBrain Researchpt_BR
dc.subjectRats – Gonadal steroid hormonespt_BR
dc.subjectHormone antagonistspt_BR
dc.subjectNitric oxidept_BR
dc.subjectRatos – Hormônios esteroides gonadaispt_BR
dc.subjectAntagonistas de hormôniospt_BR
dc.subjectÓxido nítricopt_BR
dc.titleEstrogen, but not progesterone, induces the activity of nitric oxide synthase within the medial preoptic area in female ratspt_BR
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