5HT PRESYNAPTIC INHIBITION OF RETINAL INPUT TO THE SCN

描述（申请人摘要）：本研究的目标是提供一个 了解复杂的神经基板的调节， 昼夜节律振荡器位于下丘脑视交叉上核（SCN）， 就像我们的生物钟一样。增加对功能的了解 下丘脑和昼夜节律计时系统的组织与 主要的公共卫生问题，如睡眠障碍，睡眠中断（如在 时差或轮班工作），以及严重的情感障碍。光信息 传达了SCN生物钟每日重置所必需的信息 从视网膜经由视网膜下丘脑束直接到达SCN。的SCN 也接受来自中脑中缝的密集的多巴胺能神经支配 以及来自膝状体间小叶（IGL）的额外传入。近几 多年来，已经描述了多种5-羟色胺（5-HT）受体亚型， 分为几个家族：5-HT 1 - 5-HT 7。在本提案中，我们将测试 5-HT 1B受体位于IGL末端的假说 5-HT 7受体存在于SCN神经元上， SCN中的GABA能终末。此外，我们将检验以下假设： 5-HT 1B受体不位于视网膜神经节细胞的亚群上， 向SCN和IGL发出轴突分支。电镜 免疫细胞化学技术将被用来测试的假设，5-HT 1B 5-HT 7受体位于SCN中IGL末端的突触前， 位于SCN中的神经元上和突触前GABA终末上。在 将使用原位杂交来检验IGL神经元表达 5-HT 1B受体mRNA。使用全细胞膜片钳技术，我们将测试 5-HT 7受体激动剂抑制视神经刺激诱发的视神经损伤的假说 野生型和5-HT 1A受体敲除的体外SCN神经元中的EPSC 这些相同的激动剂抑制GABA的释放在SCN通过一个 突触前机制昼夜节律的行为药理学分析 轮跑活动将用于补充体外分析。的 使用行为、药理、形态和电生理学 方法将提供5-HT受体亚型的综合分析 在SCN中以及在调节时钟功能的SCN的传入上起作用。

DESCRIPTION (applicant's abstract): The goal of this research is to furnish an understanding of the complex neural substrates underlying the regulation of the circadian oscillator located in the hypothalamic suprachiasmatic nucleus (SCN), which functions as our biological clock. Increased knowledge of the functional organization of the hypothalamus and the circadian timing system is relevant to major public health concerns such as sleep disorders, sleep disruption (as in jet lag or shift work), and serious affective disorders. Photic information essential for the daily resetting of the SCN circadian clock is conveyed directly to the SCN from the retina via the retinohypothalamic tract. The SCN also receives a dense serotonergic innervation arising from the midbrain raphe and additional afferents from the intergeniculate leaflet (IGL). In recent years, multiple serotonin (5-HT) receptor subtypes have been described and grouped into several families: 5-HT1 - 5-HT7. In this proposal, we will test the hypotheses that 5-HT1B receptors are located on the terminals of IGL afferents in the SCN and that 5-HT7 receptors are present on SCN neurons and on GABAergic terminals in the SCN. Moreover, we will test the hypothesis that 5-HT1B receptors are not located on a subset of retinal ganglion cells that send axonal branches to the SCN and IGL. Electron microscopic immunocytochemical techniques will be used to test the hypotheses that 5-HT1B receptors are presynaptic on IGL terminals in the SCN and that 5-HT7 receptors are located on neurons and presynaptically on GABA terminals in the SCN. In situ hybridization will be used to test the hypothesis that IGL neurons express 5-HT1B receptor mRNA. Using whole-cell patch-clamp techniques, we will test the hypothesis that 5-HT7 receptor agonists inhibit optic nerve stimulation-evoked EPSCs in SCN neurons in vitro in wild-type and in 5-HTlA receptor knock-out mice and that these same agonists inhibit GABA release in the SCN via a presynaptic mechanism. Behavioral pharmacological analyses of circadian wheel-running activity will be used to complement the in vitro analysis. The use of behavioral, pharmacological, morphological, and electrophysiological approaches will provide an integrated analysis of 5-HT receptor subtype function in the SCN and on afferents to the SCN that regulate clock function.