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).&nbsp;

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

Background: The orexin (OX) is a hypothalamic neuropeptide that exists in two forms, orexin A (OXA) and orexin B (OXB), which bind two receptors (OX1 and OX2). While orexin B shows selectivity for OX2, OXA is potent at both receptors. Orexins are also reported in other mammalian organs where they undergo many regulatory functions. However, their detection in the dromedary camel reproductive organs remains to be revealed. 
 
Methods: We investigated the immunoreactivity of orexin OXA and OX1 in the testis of young (6-12 month), pre-pubertal (2-3 years) and adult (6-15 years) dromedary camels. We also studied the relative expression of hypocretin neuropeptide precursor (HCRT) in the testicular tissue of these age groups. 
 
Result: Positive immunoreactions of OXA and OX1 were shown in both the tubules and interstitium of dromedary camel testis in the young animals. While positive OXA and OX1 immune-labeling was detected in the spermatogonia, Sertoli cells and Leydig cells in all ages, adult camels also showed positive OXA and OX1 signals in the primary spermatocytes, spermatozoa and interstitial blood vessels. In testes at pre-pubertal and adult stages, spermatogenic cells, Sertoli cells and Leydig cells showed stronger OXA and OX1 reactions than in young camels. Real time PCR analysis also revealed that HCRT was expressed in the testis of dromedary camels with minimal expression in young camels. In conclusion, the current study provides the first evidence for the presence of OXA and OX1 in the testis of adult and younger dromedary camels. Before puberty, the binding of OXA and OX1 in the camel testis might be important for development and proliferation of spermatogenic cells, Sertoli cells and Leydig cells; in adult animals they may play a role in steroidogenesis and spermatogenesis.

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

Age-related Localization and Expression of Orexin A and its Receptor 1 in Dromedary Camel Testis

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