Supplementary Material for: Involvement of the Orexin System in Adrenal Sympathetic Regulation

Orexin (hypocretin) is a neuropeptide secreted from hypothalamic neurons that is known to be activated during motivated behaviors and active waking. Presently, our knowledge of orexin is mainly limited to the central nervous system, and the involvement of the orexin system in peripheral tissues has received little attention. In the present study, we analyzed the existence of the orexin system in the adrenal medulla, which is part of the sympathetic nervous system. Orexin and its receptors are expressed in the bovine adrenal medulla. Orexins stimulated intracellular calcium changes and epinephrine release from cultured bovine adrenal medullary cells. Applied orexin decreased expression of prepro-orexin, orexin receptor-1 and orexin receptor-2, suggesting negative feedback regulation in the adrenal gland. Our results indicate involvement of the orexin system in the sympathetic regulation of the adrenal medulla.食欲素（Orexin，又称hypocretin）是由下丘脑神经元（hypothalamic neurons）分泌的一种神经肽（neuropeptide），已知其在动机性行为（motivated behaviors）与觉醒活跃状态（active waking）下被激活。当前学界对食欲素的认知主要局限于中枢神经系统（central nervous system），而食欲素系统在外周组织（peripheral tissues）中的作用却鲜有关注。本研究针对作为交感神经系统（sympathetic nervous system）组成部分的肾上腺髓质（adrenal medulla）中食欲素系统的存在情况展开分析。研究发现，牛肾上腺髓质中存在食欲素及其受体的表达。食欲素可刺激体外培养的牛肾上腺髓质细胞发生细胞内钙变化（intracellular calcium changes）并释放肾上腺素（epinephrine）。外源性给予食欲素会下调前促食欲素原（prepro-orexin）、食欲素受体1（orexin receptor-1）与食欲素受体2（orexin receptor-2）的表达，这提示肾上腺内存在负反馈调控（negative feedback regulation）机制。本研究结果表明，食欲素系统参与肾上腺髓质的交感神经调控。