Distribution Of Orexin In Rabbit

Orexins are neuropeptides found in 1998, which consist of two piptides, orexin A and orexin B. Orexins are involved in a number of biological functions including feeding, energy balance, sleep-wake cycle, visceral activity and endocretin through its two specific G protein coupled receptors. Distribution of orexins in rat, pig and sheep has been reported, but not in rabbit. Therefore, localization of orexins in rabbit was studied by immunohistochemistry. The results are as follows.1 Localization of orexin A in rabbitThe results show that orexin A-like immunoreactive (OXA-IR) cells were observed in the hypothalamus, subthalamus, testis, pancreas, gastric pylorus, samll intestine, large intestine and adrenal gland. In the hypothalamus, OXA-IR neurons are present in the paraventricular nucleus, supraoptic nucleus, dorsomedial nucleus, perifornical nucleus, anterior hypothalamic area, lateral hypothalamic area and posterior hypothalamic area with the majority in dorsomedial nucleus, perifornical nucleus and lateral hypothalamic area and the minority in supraoptic nucleus and anterior area. Sparse OXA-IR neuron was also observed in the zona incerta (ZI) of the subthalamus. In contrast, OXA-immunoreactive fibers are distributed widespreadly in the central nervous system (CNS), with dense distribution in the hypothalamus, pituitary posterior lobe , midline nuclear group of thalamus, habenular nucleus, nucleus of solitary tract, locus coeruleus, perivenricules area, and spinal cord. In the periphery organs, OXA-IR cells were found in the mesenchyme of the testis, pancreatic islet, the lamina propria of the pylorus and large intestine, the epithelial lamina of and the lamina propria of the samll intestine and the zona reticularis of adrenal cortex. No OXA-IR was detected in the heart, liver, spleen, thyroid gland, kidney and ovary.2 Localization of orexin B in rabbitThe results show that orexin B-like immunoreactive (OXB-IR) cells were observed in the hypothalamus, subthalamus, testis, small intestine and large intestine. In the hypothalamus, OXB-IR neurons are present in the paraventricular nucleus, dorsomedial nucleus, perifornical nucleus, and lateral hypothalamic area and posteriorhypothalamic area and with the majority in the dorsomedial nucleus, perifomical nucleus, and lateral hypothalamic area and the minority in the paraventricular nucleus and posterior hypothalamic area. Sparse OXB-IR neuron was also observed in the ZI of the subthalamus. OXB-immunoreactive fibers are distributed widespreadly in the CNS, with dense distibution in the hypothalamus, midline nuclear group of thalamus, locus coeruleus, and spinal cord. In the periphery organs, OXB-IR cells were found in the mesenchyme of testis, the lamina propria of and the epithelial lamina of small intestine and the lamina propria of large intestine. No OXB-IR was detected in the heart, liver, spleen, stomach, kidney, adrenal gland, thyreoid and ovary.3 Similar and different distribution of orexin A and orexin B in the rabbitIn the hypothalamus, OXA-IR and OXB-IR cells were both observed in the paraventricular nucleus, dorsomedial nucleus, perifomical nucleus, lateral hypothalamic area and posterior hypothalamic area. However, only orexin A-IR cells were found in the supraoptic nucleus and anterior hypothalamic area.OXA-IR and OXB-IR fibers were both distributed widespreadly In the CNS, but relative density of OXB-IR fibers were lower than that of OXA-IR fibers in the some areas such as pituitary posterior lobe, nucleus of solitary tract and reticular formation.In the periphery organs, OXA-IR and OXB-IR cells were both observed in the testis, small intestine and large intestine. However, only OXA-IR cells were found in the pancreas, adrends gland and stomach. No OXA-IR and OXB-IR cells were both observed in the ovary, which shows difference in distribution of orexin in genital gland between of female and male rabbits.Our results were similar to those obtained in pig, rodents and sheep with some differences. The results provide morphological evidence for understanding...