P>Objective To investigate the possible role of orexin in reproduction and examine the changes in the expression of orexin and its receptors (OX1R, OX2R) in the rat hypothalamus during pregnancy, parturition and lactation. Methods The expressions of preproorexin (preproOX), orexinA, OX1R, and OX2R in the rat hypothalamus during pregnancy, parturition, and lactation were evaluated by competitive reverse transcriptionpolymerase chain reaction (RTPCR) and immunohistochemistry assay. Results OrexinA immunoreactive (ir) neurons and the OX1R subtype in neuronal cell bodies were mainly located in the lateral hypothalamic area (LHA) as well as in the magnocellular neurons of the paraventricular and supraoptic nuclei respectively in pregnant and lactating rats. The preproOX and OX1R mRNA levels on the 1st day of lactation were significantly higher than that during late pregnancy and lactation. No significant changes of OX2R expression were observed during the various reproductive phases. Conclusion Orexin might be involved in regulating reproductive func