SUPRACHIASMATIC NUCLEI-NEUROBIOLOGY OF A CIRCADIAN CLOCK

昼夜节律是一种天生的计时能力的明显表现 机制，即，一种“生物钟”。“对临床和 人类昼夜节律计时系统的实际重要性正在增加， 紊乱的生物钟功能可能是一些症状的基础， 神经精神疾病 这项研究计划提出了一项调查 啮齿类动物中假定的昼夜节律起搏器的基本神经生物学， 下丘脑前部的视交叉上核（SCN）。 一个 实验方法，允许连续输液 可逆药理学探针进入SCN的未麻醉和 14天的自由啮齿动物。 这种设计允许系统评估 以及昼夜节律系统的三个组成部分的区别 体内：环境光暗夹带的输入途径 周期，实际上产生昼夜节律振荡的起搏器， 一种表达明显的、可测量的节律的输出途径。 在 使用这种方法的初步研究，河豚毒素（TTX）注入 进入大鼠的SCN。 TTX阻断了输入和输出功能 路径而不干扰内部计时机制 起搏器 钠离子依赖性动作电位需要的夹带 和表达明显的昼夜节律，但不是必需的， 起搏器保持时间。 第一组拟议的实验更充分地描述了影响 慢性TTX注入SCN 地形特异性是 描绘，电生理测定开发，行为 范式被细化和扩展，另一个输出（昼夜节律 精氨酸加压素）和其他输入（ 由卡巴胆碱或神经肽Y介导）。 这些研究有助于 验证和扩展实验方法作为一个普遍有用的工具 用于进一步的药理学研究。 第二组实验测试一般效用和适用性 的实验方法作为一种体内测定系统， 除TTX外的其他探针。 为了测试这一策略，有两个协议 建议确定电压依赖性Ca2+通道或膜 电位可能与起搏器的内部机制有关， 的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 葡萄糖利用率（通过14C标记的脱氧葡萄糖技术测量） 被评估。

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.