Impact of the Proestrous Milieu on the Expression of Orexin Receptors and Prepro-Orexin in Rat Hypothalamus and Hypophysis. Actions of Cetrorelix and Nembutal

SILVEYRA, P; CATALANO, P. N; LUX-LANTOS VA; LIBERTUN C

AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM

The Society of Physiology

Lugar: Bethesda MD; Año: 2007 vol. 292 p. 820 - 828

0193-1849

Orexins and their receptors OX1 and OX2 regulate energy balance and sleep-wake cycle.We studied the expression of prepro-orexin (PPO), OX1 and OX2 in brain and pituitaryunder the influence of the hormonal status in adult rats. Primarily, PPO, OX1 and OX2expression was determined in Sprague-Dawley female cycling rats during proestrus and inmales. Animals were sacrificed at two hours intervals. Anterior (AH) and mediobasal(MBH) hypothalamus, anterior pituitary (P) and frontoparietal cortex (CC), werehomogenized in TRIzol and mRNAs obtained for screening of PPO, OX1, OX2 expressionby semiquantitative RT-PCR. Main findings were confirmed and extended to all days of thecycle by quantitative real-time RT-PCR. Hormones and food consumption weredetermined. Finally, OX1, OX2 and PPO were measured by real-time RT-PCR in tissuescollected at 19:00 h of proestrus after treatments at 14:00 h with ovulation blocking agents,Cetrorelix or Pentobarbital.OX1 and OX2 expression increased at least three-fold in AH, MBH and P, but not in CC,between 17:00 h and 23:00 h of proestrus, without variations in estrus, diestrus or males.PPO in AH and MBH showed a four-fold or higher increase only during proestrousafternoon. Cetrorelix or Pentobarbital prevented increases of OX1 and OX2 only in thepituitary and blunted gonadotropin surges, but left OX1, OX2 and PPO brain expressionunchanged.Reproduction, energy balance and sleep-wake cycle are integrated. Here we demonstratethat in the physiological neuroendocrine condition leading to ovulation, information to theorexinergic system acts in hypothalamus and pituitary by different mechanisms.