SUPRACHIASMATIC NUCLEI-NEUROBIOLOGY OF A CIRCADIAN CLOCK

昼夜节律性是天生守时的明显表现。 机制，即“生物钟”。对临床和临床的再认识 人类昼夜节律计时系统的实际重要性正在增加， 而紊乱的时钟功能可能是许多 神经精神疾病。这项研究计划提出了一项调查 对啮齿动物体内可能存在的昼夜节律起搏器的基本神经生物学的研究， 下丘脑前部的视交叉上核(SCN)。一个 提出了一种实验方法，允许持续输注 未麻醉大鼠脊髓束核的可逆性药理学研究 无拘无束的啮齿动物14天。此设计允许进行系统评估 并区分起作用的生理系统的三个组成部分 体内：环境明暗夹带的输入途径 周期，一种实际产生昼夜振荡的起搏器，以及 一种表达公开的、可测量的节奏的输出途径。在……里面 使用这种方法的初步研究，注入河豚毒素(TTX) 进入大鼠的SCN。TTX阻塞了输入和输出功能 在不干扰时钟的内部计时机制的情况下 起搏器。携带需要依赖于钠的动作电位。 和表达明显的昼夜节律，但不需要 起搏器，以保持节拍。 第一组拟议的实验更充分地描述了这些效应 慢性TTX注射到SCN。地形特异度是 描述了，开发了一种电生理测试，即行为 范式是精炼和扩展的，另一种输出(昼夜节律 脑脊液中的精氨酸加压素)和其他输入(那些 由氨基甲酰胆碱或神经肽Y介导)。这些研究是有帮助的 验证和扩展实验方法作为一种普遍有用的工具 用于进一步的药理学研究。 第二组实验测试了通用的实用性和适用性 作为体内药理检测系统的实验方法 TTX以外的探头。为了测试这一策略，有两个协议 建议确定电压依赖的钙通道或膜 电位可能与起搏器的内部机制有关 SCN。 第三组实验开始定义负责 SCN能量代谢的昼夜节律。河豚毒素对SCN的影响 葡萄糖利用(用~(14)C标记脱氧葡萄糖技术测量) 是经过评估的。

Circadian rhythmicity is the overt manifestation of an innate timekeeping mechanism, i.e., a "circadian clock." Recognition of the clinical and practical importance of the human circadian timing system is increasing, and disordered clock function may underlie the symptoms of a number of neuropsychiatric illnesses. This research plan proposes an investigation into the basic neurobiology of a putative circadian pacemaker in rodents, the suprachiasmatic nuclei (SCN) in the anterior hypothalamus. An experimental approach is presented that permits continuous infusion of reversible pharmacological probes into the SCN of unanesthetized and unrestrained rodents for 14 days. This design allows systematic assessment and distinction of the three components of a functioning circadian system in vivo: an input pathway for entrainment to the environmental light-dark cycle, a pacemaker that actually generates the circadian oscillation, and an output pathway for expression of overt, measurable rhythms. In preliminary studies using this approach, tetrodotoxin (TTX) was infused into the SCN of rats. TTX blocked the function of both input and output pathways without disturbing the internal timekeeping mechanism of the pacemaker. Na+-dependent action potentials are needed for the entrainment and expression of overt circadian rhythms but are not required for the pacemaker to keep time. The first set of proposed experiments more fully characterizes the effects of chronic TTX infusion into the SCN. Topographical specificity is delineated, an electrophysiological assay is developed, the behavioral paradigm is refined and extended, and another output (the circadian rhythm of arginine vasopressin in cerebrospinal fluid) and other inputs (those mediated by carbachol or neuropeptide Y) are assayed. These studies help to validate and extend the experimental approach as a generally useful tool for further pharmacological studies. The second set of experiments tests the general utility and applicability of the experimental approach as an in vivo assay system for pharmacological probes other than TTX. To put this strategy to the test, two protocols are proposed to determine whether voltage-dependent Ca2+ channels or membrane potential can be implicated in the internal mechanism of the pacemaker in the SCN. The third set of experiments begins to define the processes responsible for the circadian rhythm of SCN energy metabolism. The effects of TTX on SCN glucose utilization (measured by the 14C-labeled deoxyglucose technique) are assessed.