title: Release of norepinephrine in the preoptic area activates anteroventral periventricular nucleus neurons and stimulates the surge of luteinizing hormone.
abstract: The role of norepinephrine (NE) in regulation of LH is still controversial. We investigated the role played by NE in the positive feedback of estradiol and progesterone. Ovarian-steroid control over NE release in the preoptic area (POA) was determined using microdialysis. Compared with ovariectomized (OVX) rats, estradiol-treated OVX (OVX+E) rats displayed lower release of NE in the morning but increased release coincident with the afternoon surge of LH. OVX rats treated with estradiol and progesterone (OVX+EP) exhibited markedly greater NE release than OVX+E rats, and amplification of the LH surge. The effect of NE on LH secretion was confirmed using reverse microdialysis. The LH surge and c-Fos expression in anteroventral periventricular nucleus neurons were significantly increased in OVX+E rats dialyzed with 100 nm NE in the POA. After Fluoro-Gold injection in the POA, c-Fos expression in Fluoro-Gold/tyrosine hydroxylase-immunoreactive neurons increased during the afternoon in the A2 of both OVX+E and OVX+EP rats, in the locus coeruleus (LC) of OVX+EP rats, but was unchanged in the A1. The selective lesion of LC terminals, by intracerebroventricular N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, reduced the surge of LH in OVX+EP but not in OVX+E rats. Thus, estradiol and progesterone activate A2 and LC neurons, respectively, and this is associated with the increased release of NE in the POA and the magnitude of the LH surge. NE stimulates LH secretion, at least in part, through activation of anteroventral periventricular neurons. These findings contribute to elucidation of the role played by NE during the positive feedback of ovarian steroids.
authors.affiliation: Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, 31270-901, Belo Horizonte, Minas Gerais, Brazil. reszawka@icb.ufmg.br
authors.forename: Raphael E
authors.initials: RE
authors.lastname: Szawka
authors.forename: Maristela O
authors.initials: MO
authors.lastname: Poletini
authors.forename: Cristiane M
authors.initials: CM
authors.lastname: Leite
authors.forename: Marcelo P
authors.initials: MP
authors.lastname: Bernuci
authors.forename: Bruna
authors.initials: B
authors.lastname: Kalil
authors.forename: Leonardo B D
authors.initials: LB
authors.lastname: Mendonça
authors.forename: Ruither O G
authors.initials: RO
authors.lastname: Carolino
authors.forename: Cleyde V V
authors.initials: CV
authors.lastname: Helena
authors.forename: Richard
authors.initials: R
authors.lastname: Bertram
authors.forename: Celso R
authors.initials: CR
authors.lastname: Franci
authors.forename: Janete A
authors.initials: JA
authors.lastname: Anselmo-Franci
mesh_terms: D000818:Animals; D020643:Anterior Thalamic Nuclei / Q000187:drug effects* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000378:metabolism*; D017551:Microdialysis; D009638:Norepinephrine / Q000494:pharmacology*; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar
chemical_list: D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D009638:Norepinephrine