Calcium Signaling in Suprachiasmatic Nucleus Neurons

视交叉上核神经元中的钙信号传导

基本信息

批准号：
6765721
负责人：
Charles N Allen
金额：
$ 27.14万
依托单位：
OREGON HEALTH & SCIENCE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2004
资助国家：
美国
起止时间：
2004-03-01 至 2009-02-28
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Disturbances in circadian rhythms contribute to a variety of diseases and impair mental and physical performance. Circadian rhythms in physiological and behavioral processes are generated by a molecular clock located in the suprachiasmatic nucleus. This clock receives environmental information from cues such as light and subsequently creates timing information that is sent to the rest of the organism. While the signaling pathways involved in this chain of information are poorly understood, evidence suggests a possible role for Ca2+ as a signaling molecule for both input to and output from the circadian clock. But the source of this Ca2+ is unknown. One model proposes that glutamate released from terminals of the retinohypothalamic tract activates NMDA receptors, which generate nitric oxide and release Ca2+ from ryanodine-sensitive stores. However, the release of Ca2+ from ryanodine-sensitive stores by glutamate or nitric oxide has not been directly demonstrated. NMDA receptor activation increases the nuclear Ca2+ concentration of SCN neurons. Nuclear Ca2+ regulates gene expression, including possibly clock gene expression. The long-term goal of this work is to characterize the functional properties of SCN neurons and how the circadian clock regulates these properties. This proposal will determine the roles that cytoplasmic and nuclear Ca2+ play as circadian input and output signals. Our central hypothesis is that changes in cytoplasmic and nuclear Ca2+ concentration are a critical step in light's regulation of the circadian clock. This proposal uses an innovative combination of fluorescent imaging techniques, cell culture, and electrophysiological recording techniques to study the regulation of Ca2+ in SCN neurons during different portions of the circadian day. This research will identify the early steps in the light-signaling pathway. The Specific Aims of the proposal are: 1) Identify the mechanisms and circadian regulation of the increase of the cytoplasmic Ca2+ concentration produced by activating NMDA and AMPA receptors. 2) Determine the mechanisms and circadian phase dependence of the increase in the nuclear Ca2+ concentration produced by NMDA receptor activation. 3) Determine the role that PACAP plays in regulating changes in the cytoplasmic and nuclear Ca2+ concentration induced by NMDA and AMPA receptor activation. 4) Investigate whether the peak of the cytoplasmic Ca2+ rhythm precedes the peak of action potential firing frequency rhythm in SCN neurons. Together, these experiments will identify the early steps in the light-signaling pathway, thus contributing to a better understanding of the cellular basis of circadian rhythms.

描述（由申请人提供）：昼夜节律紊乱会导致多种疾病并损害精神和身体机能。生理和行为过程中的昼夜节律是由位于视交叉上核的分子钟产生的。该时钟从光等线索接收环境信息，随后创建发送到生物体其他部分的计时信息。虽然对这条信息链中涉及的信号通路知之甚少，但有证据表明 Ca2+ 作为生物钟输入和输出的信号分子可能发挥作用。但这种 Ca2+ 的来源尚不清楚。一个模型提出，从视网膜下丘脑束末端释放的谷氨酸会激活 NMDA 受体，从而产生一氧化氮并从兰尼碱敏感储备中释放 Ca2+。然而，尚未直接证明谷氨酸或一氧化氮从兰尼碱敏感储备中释放 Ca2+。 NMDA 受体激活增加 SCN 神经元的核 Ca2+ 浓度。核 Ca2+ 调节基因表达，可能包括时钟基因表达。这项工作的长期目标是表征 SCN 神经元的功能特性以及生物钟如何调节这些特性。该提案将确定细胞质和细胞核 Ca2+ 作为昼夜节律输入和输出信号的作用。我们的中心假设是细胞质和细胞核 Ca2+ 浓度的变化是光调节生物钟的关键步骤。该提案采用荧光成像技术、细胞培养和电生理记录技术的创新组合来研究昼夜节律的不同部分期间 SCN 神经元中 Ca2+ 的调节。这项研究将确定光信号通路的早期步骤。该提案的具体目标是： 1) 确定通过激活 NMDA 和 AMPA 受体产生的细胞质 Ca2+ 浓度增加的机制和昼夜节律调节。 2)确定NMDA受体激活产生的核Ca2+浓度增加的机制和昼夜节律相位依赖性。 3)确定PACAP在调节NMDA和AMPA受体激活引起的细胞质和细胞核Ca2+浓度变化中所起的作用。 4) 研究SCN神经元细胞质Ca2+节律的峰值是否先于动作电位放电频率节律的峰值。这些实验将共同确定光信号通路的早期步骤，从而有助于更好地理解昼夜节律的细胞基础。