INTRISIC NEUROMODULATION OF A SMALL NEURONAL NETWORK

描述（申请人提供）：神经调节，神经元和突触性质的神经化学改变，对运动模式的产生和行为可塑性很重要，但很少有研究探索神经回路中神经调节信号的动力学。该项目的目标是了解细胞内信号介导的神经调节作用是如何随着时间的推移而动态整合的，以及这如何有助于运动行为的产生和可塑性。所研究的系统是腹足类软体动物Tritonia diomedea节律性逃避游泳反应的中枢模式发生器（CPG）。该模型系统特别适合解决这些问题，因为它包含CPG回路固有的已识别神经元，这些神经元使用5-羟色胺（5-HT）在其他CPG神经元中唤起神经调节作用。提出的实验验证了由这种“内在神经调节”引起的第二信使信号的动态在运动模式的产生中起直接作用，第二信使信号的汇总有助于行为的终止和习惯化的假设。目的一是可视化ca2 +和cAMP在运动模式产生过程中的时间动态。目的2是确定哪些第二信使介导特定的神经调节作用的5-羟色胺和血清素能神经元。目的3是测试动态生化信号在运动模式产生和可塑性中的行为作用。实验方法包括电生理和光学记录原位和原代细胞培养。使用荧光指示器的共聚焦和多光子成像测量ca2 +和cAMP水平的实时变化。第二信使被操纵的药理学和实时快速光解笼中的化合物。目标是在运动行为产生过程中直接观察和扰动动态生化信号。这些实验将阐明神经调节信号如何在行为相关的时间尺度上进行时间整合的一般原理，从而将神经元网络的运作与细胞内生化信号网络结合起来。了解运动系统中生物胺信号传导的神经调节机制的动力学，可能对与胺能信号传导缺陷相关的疾病（如帕金森病和亨廷顿病）具有重要意义。

DESCRIPTION (provided by applicant): Neuromodulation, the neurochemical alteration of neuronal and synaptic properties, is important for motor pattern generation and behavioral plasticity, yet few studies have explored the dynamics of neuromodulatory signaling in neuronal circuits. The goals of this project are to understand how intracellular signals mediating neuromodulatory actions are dynamically integrated over time and how this contributes to the production and plasticity of a motor behavior. The system being studied is the central pattern generator (CPG) underlying the rhythmic escape swimming response of the gastropod mollusc, Tritonia diomedea. This model system is uniquely suited to address these issues because it contains identified neurons, intrinsic to the CPG circuit, that use serotonin (5-HT) to evoke neuromodulatory actions in other CPG neurons. The proposed experiments test the hypotheses that the dynamics of 2nd messenger signaling evoked by this "intrinsic neuromodulation" play a direct role in motor pattern production and that summation of 2nd messenger signals contributes to termination of the behavior and to its habituation. Aim I is to visualize the temporal dynamics of Ca 2+ and cAMP during motor pattern production. Aim 2 is to identify which second messengers mediate particular neuromodulatory actions of 5-HT and serotonergic neurons. Aim 3 is to test the behavioral roles of dynamic biochemical signaling during motor pattern generation and plasticity. The experimental methods include electrophysiological and optical recordings in situ and in primary cell culture. Real-time changes in Ca 2+ and cAMP levels are measured using confocal and multiphoton imaging of fluorescent indicators. Second messengers are manipulated both pharmacologically and in real time with rapid photolysis of caged compounds. The objective is to directly observe and perturb dynamic biochemical signals during the production of the motor behavior. These experiments will elucidate general principles of how neuromodulatory signals are temporally integrated over behaviorally relevant time scales, thereby uniting the operation of neuronal networks with intracellular biochemical signaling networks. Understanding the dynamics of neuromodulatory mechanisms underlying signaling by biogenic amines in a motor system is likely to have significance for diseases related to defects in aminergic signaling such as Parkinson's disease and Huntington's disease.