CHOLINERGIC INFLUENCE ON CIRCADIAN FUNCTION

所有哺乳动物都有一个生物钟，它控制着生物体的神经、激素和代谢功能的日常振荡，几乎有24小时的周期。大脑下丘脑内的视交叉上核(SCN)容纳了这个时钟。SCN与大脑的不同区域有神经联系。在这些连接中，突出的是来自大脑负责睡眠和警觉的区域的胆碱能投射，即基底前脑(BF)和脑干。关于SCN内的细胞内信号转导通路，有相当多的工作可用。体外药理研究表明，M_1AChR的M1亚型是介导胆碱类药物对昼夜节律系统影响的受体。最近，国际药理学联合会受体命名和药物分类委员会对涉及M1AChR的药物在胆碱能信号级联中的特异性提出了质疑。代替特定的药理学，必须使用其他方法来确定介导胆碱能昼夜节律信号的受体(S)。在这项提案中，将在缺乏M1AChR(M1KO)的小鼠身上进行电生理、行为和解剖学研究。首先，B6129PF1/J小鼠，一种与M1K0具有相似遗传背景的小鼠，将在体外和体内进行胆碱能激动剂卡巴胆碱的敏感性测试。其次，将测试M1KO对氨基甲酸乙酯的敏感性降低。最后，将使用双标记荧光共聚焦显微镜来评估SCN内的胆碱能终末是否与含有M1AChR的细胞并列并绘制其分布图。

All mammals possess a circadian clock that governs daily oscillations with neural, hormonal, and metabolic functions for the organism with a near 24-h period. The suprachiasmatic nucleus (SCN) within the brain's hypothalamus houses this clock. The SCN has neural connections with various regions of the brain. Prominent among these connections are cholinergic projections from regions of the brain responsible for asleep and alerting, namely the basal forebrain (BF) and brainstem. A considerable body of work is available regarding intracellular signal transduction pathways within SCN. Pharmacological studies in vitro have implicated the M1-subtype of the muscarinic acetylcholine receptor (M1AChR) as the receptor mediating the effects of cholinergics on the circadian system. Recently, the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification has questioned the specificity of the drugs used to implicate the M1AChR in the cholinergic signaling cascade. In lieu of specific pharmacology, other methods must be employed to confidently identify the receptor(s) mediating cholinergic circadian signaling. In this proposal, electrophysiological, behavioral and anatomical studies will be carried out in mice devoid of the M1AChR (M1KO). First, the B6129PF1/J mouse, a mouse of similar genetic background to the M1K0, will be tested for sensitivity to the cholinergic agonist, carbachol, both in vitro and in vivo. Second, the M1KO will be tested for decreased sensitivity to carbachol. Finally, double-label fluorescence confocal microscopy will be used to evaluate whether the cholinergic terminals within the SCN are juxtaposed to M1AChR-containing cells and to map their distribution.