Expression of orexin receptors 1 (OX1) and 2 (OX2) in hypothalamus and adenohypophysis in cycling female and male rats.

CARLOS LIBERTUN, PATRICIA SILVEYRA, PAOLO N. CATALANO, VICTORIA LUX-LANTOS.

Pittsburg, Pennsylvania, USA.

Congreso; Sixth International Congress of Neuroendocrinology; 2006

The International Neuroendocrine Federation

Orexins A and B, and their G-protein coupled receptors, play a role in energy balance and the sleep-wake cycle. Here, we studied whether both receptors are related with brain control of reproductive functions. Regular cycling 60 day old female Sprague–Dawley rats were decapitated at 2 h intervals, starting at 09:00 until 23:00 h, during diestrus, proestrus, and estrus (lights on from 07:00 to 19:00 h). A group of males of the same age was also studied. Anterior (AH) and mediobasal hypothalamus (MBH), adenohypophysis (H) and frontoparietal cortex (CC), as control, were dissected and homogenized in TRIzol for later determination of OX1 and OX2 expression by RT-PCR; in representative samples, findings were confirmed by real time PCR of OX1. Trunk blood was collected for RIA determinations of pituitary and ovary hormones. OX1 and OX2 expression increased in AH, MBH, and H, but not in CC, at 19:00 h, during darkness, only during proestrus but not in estrus, diestrus or in male rats. FSH, LH, estradiol, and progesterone in females, and testosterone in males, followed the expected normal patterns of the colony (peaked during afternoon of proestrus after 17:00 h). The fact that the increase of orexin receptor expression occurs selectively in hypothalamus and pituitary, and only in females during proestrous, suggest that they are related with the hormonal status of proestrus but not with the dark–light cycle. (Supported by CONICET, ANPCYT, and UBA, Argentina).