Immunohistochemical localization of orexin-B, orexin-1 receptor, ghrelin, GHS-R in the lacrimal gland of normal and diabetic rats

Orexin-B, ghrelin and their receptors play an important role in the regulation of feeding in mammals. The pattern of distribution of orexin-B, orexin-1-receptor (OX1R), ghrelin and growth hormone secretagogue receptor (GHS-R) in the lacrimal gland of normal and diabetic rats has not been reported. Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ) at 60 mg kg−1. Forty weeks after the induction of STZ-induced diabetes, normal, age-matched controls and diabetic rats were anesthetized with chloral hydrate (intraperitoneally) and their lacrimal glands removed and processed for immunofluorescence. Orexin-B was observed in the cells localized to the interacinar regions while OX1R was discerned in the nerves innervating the wall of small blood vessels. Ghrelin was also present in a group of cells located in the periacinar regions of the lacrimal glands of normal and diabetic rats. In contrast, GHS-R was observed in the apical region of the ductal cells of the lacrimal glands of both normal and diabetic rats. The pattern of distribution of these orexigenic peptides and their receptors did not significantly change after the onset of diabetes. In conclusion, orexin-B, ghrelin and their receptors are present in the lacrimal glands of both normal and diabetic rats and may play a role in the regulation of lacrimal gland function.