Localization of Orexin and its Receptor in Corpus Luteum and in vitro Effect of Orexin on Progesterone Production from Luteal Cells in Buffalo

Background: Orexin is a hypothalamic neuropeptide involved in regulating various biological functions, including reproduction. The study aimed to investigate the immunolocalization of orexin and its receptors in the corpus luteum in buffalo (Bubalus bubalis) ovary and the effect of orexin on progesterone production.Methods: The study was carried out on buffalo ovaries, each with a different developmental stage of corpus luteum (CL) (n=10 for each stage). The CLs were separated out from ovaries for immunolocalization of orexin and its receptors in CL. In the in vitro study, luteal cells were cultured and treated with recombinant orexin at 0.1, 1 and 10 ng/mL doses for 48 h and P4 concentration in the spent media was determined by ELISA.Result: Results of the present study revealed that orexin and its receptors are localized in the cytoplasm of large and small luteal cells of CL. The immunoreactivity varied with a stage-specific difference in CL. The present study also revealed that orexin inhibits P4 production in cultured luteal cells. The findings indicate orexin affects luteal dynamics and reproductive functions in buffalo (Bubalus bubalis).