Int.J.Curr.Microbiol.App.Sci (2020) 9(11): 1268-1276 1268 Original Research Article https://doi.org/10.20546/ijcmas.2020.911.148 Expression Profile of Orexin System in Corpus Luteum of Buffalo during Estrous Cycle V. M. Sardar 1 , Mahesh Gupta 1* , J. P. Korde 1 , K. B. Bahiram 1 , K. P. Bambode 1 and S. W. Bonde 2 1 Department of Veterinary Physiology, 2 Department of Veterinary Biochemistry, Nagpur Veterinary College, Nagpur, India *Corresponding author ABSTRACT Introduction Reproductive cycle in mammals is characterized by sequential proliferation, differentiation and conversion of ovarian follicular cells followed by development and decay of the CL in a cyclic manner. The corpus luteum (CL) is a transitorily functioning organ and plays a key role in the regulation of the estrous cycle and in the safeguarding of pregnancy which is chiefly performed by progesterone, the main steroid hormone synthesized by CL (Stocco et al., 2007) The development, maintenances, lysis, of CL and steroid production are important events in mammalian reproduction. The CL undergoes regression after maturation and disappeared from the ovary and allowing the initiation of a new cycle. The role of pituitary gonadotropins in the process of luteal function is well recognized. However, recent studies also showed evidences of modulatory International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 9 Number 11 (2020) Journal homepage: http://www.ijcmas.com Orexin A and B are neuropeptides synthesized mainly in the lateral hypothalamus and are associated with a variety of physiological functions such as energy homeostasis, sleep and wakefulness, feeding behavior, as well as the reproductive system. The biological actions of the hormones are mediated via two distinct G protein-coupled receptors, termed orexin receptor 1 (OX1R) and orexin receptor 2 (OX2R). The aim of the current study was to investigate the gene expression of orexin and its receptors OX1R and OX2R in different stages of corpus luteum (CL) during estrous cycle in ( Bubalus bubalis). The result showed that transcript of pre-pro-orexin (PPO), OX1R and OX2R was present in buffalo CL throughout the estrous cycle however the level of transcript varied through different stages of CL. The abundance of transcript of orexin and its receptor was high higher P<0.05) in early (CL1, days 1-4) and regressing stage (CL4, days >17) of CL whereas the expression was significantly lower (P<0.05) in mid (CL2, days 5-10) and late luteal (CL3, days 11- 16) stage during estrous cycle. Presence of both ligand (orexin) and receptors (OX1R) and (OX2R) in CL of buffalo ovary suggest the autocrine and paracrine role of orexin in corpus luteum functions and indicate the role of orexin in regulation of reproductive functions in water buffalo. Keywords Orexin, Buffalo, Corpus luteum, Estrous cycle Accepted: 10 October 2020 Available Online: 10 November 2020 Article Info