SUPRACHIASMATIC NUCLEI-NEUROBIOLOGY OF A CIRCADIAN CLOCK

昼夜节律是与生俱来的计时能力的明显表现 机制，即“生物钟”。 临床和治疗的认可 人类昼夜节律计时系统的实际重要性正在增加， 时钟功能紊乱可能是许多症状的根源 神经精神疾病。 本研究计划提出一项调查 研究啮齿动物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）。 安 提出了允许连续输注的实验方法 可逆药理学探针进入未麻醉和非麻醉状态下的 SCN 不受约束的啮齿动物14天。 这种设计允许系统评估 昼夜节律系统的三个组成部分的区别 体内：夹带环境明暗的输入途径 周期，实际上产生昼夜节律振荡的起搏器，以及 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，输注了河豚毒素（TTX） 进入大鼠的 SCN。 TTX 阻断输入和输出功能 路径不干扰内部计时机制 起搏器。 夹带需要 Na 依赖性动作电位 和明显的昼夜节律的表达，但不是必需的 起搏器来保持时间。 提出的第一组实验更全面地表征了效果 慢性 TTX 输注至 SCN。 地形特异性是 描述了，开发了一种电生理学测定，行为 范式被细化和扩展，另一个输出（昼夜节律） 脑脊液中的精氨酸加压素）和其他输入（那些 测定了由卡巴胆碱或神经肽Y)介导的。 这些研究有助于 验证和扩展实验方法作为普遍有用的工具 以进行进一步的药理学研究。 第二组实验测试通用性和适用性 作为药理学体内测定系统的实验方法 TTX 以外的探针。 为了测试这个策略，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 SCN。 第三组实验开始定义负责的过程 SCN能量代谢的昼夜节律。 TTX对SCN的影响 葡萄糖利用率（通过 14C 标记脱氧葡萄糖技术测量） 进行评估。

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.