BRAINSTEM CIRCUITS CONTROLLING GASTROINTESTINAL FUNCTION

描述：孤束核（NTS）和背侧核 迷走神经运动核（DMV）是神经回路的重要组成部分 负责协调迷走神经-迷走神经反射，如胃 接受性松弛和回肠制动。 最近，有人提出， 有一些离散的节点， NTS中的特定神经元与DMV神经元的不同群体。 虽然 这个概念已经被许多研究者讨论和研究过， 没有电生理学证据支持它，可能是因为 与任何体内实验相关的实质性技术困难 试图确定个体NTS和 DMV神经元。 另一方面，切片范例非常适合于此 调查的类型。 我们在本申请中描述的研究是 基于以下假设：假设1：NTS-DMV电路 以允许NTS中特定神经元相互作用的方式组织 与车管所里选定的神经元子集进行比对 我们特别建议， 内侧DMV的神经元接受来自内侧DMV的神经元的快速兴奋性输入。 cen-NTS（一种相互作用，可以为 接受性松弛反射），而DMV外侧的神经元接受 “来自com-NTS中神经元的较慢或较长持续时间的抑制性输入（ 可能在回肠制动现象中起作用的相互作用）。 假设2：延髓中缝核整合GI反射活动， 提供NTS-DMV突触的选择性调节。 拟将 这种调节是由延髓中缝神经元完成的， 抑制DMV神经元的亚群和/或通过抑制NTS神经元的亚群， 5-HT、TRH和/或SP的释放。将使用整体 包括NTS在内的脑干切片中的细胞膜片钳记录， 车管所和中缝核。 这些切片将取自 将荧光示踪剂放置在孤立的分支中， 迷走神经或胃肠道的选定区域。 这 协议将标记内脏传入的终端的子集， 终止于NTS神经元以及投射的DMV神经元的胞体 胃肠道的区域，接受荧光注射， 追踪器 将从NTS诱发突触电流和电位， 将记录在DMV和/或NTS中; DMV-NTS突触的调制 将在刺激相邻的中缝髓核时进行分析， 在用5-HT、TRH和/或SP灌注后， 具体的目标将揭示突触电流的行为背后， 离散NTS和DMV神经元群体。 此外，基本 将阐明迷走神经-迷走神经反射的回路。 这些数据将 增加我们对NTS和DMV之间如何相互作用的理解 神经元可以导致神经元活动的模式， 迷走-迷走反射，如胃感受性舒张和回肠制动。

DESCRIPTION: The nucleus of the tractus solitarius (NTS) and the dorsal motor nucleus of the vagus (DMV) are essential components of a circuit responsible for the coordination of vago-vagal reflexes such as gastric receptive relaxation and the ileal brake. Recently, it has been proposed that there are discreet nodes where sensory information is transmitted from specific neurons in the NTS to distinct populations of DMV neurons. Though this concept has been discussed and examined by a number of investigators, there is no electrophysiologic evidence to support it, likely because of substantial technical difficulties associated with any in vivo experiments that would attempt to determine the interactions between individual NTS and DMV neurons. On the other hand, slice paradigms are ideally suited to this type of investigation. The studies we describe in this application are based on the following hypotheses: Hypothesis 1: The NTS-DMV circuitry is organized in a manner that allows specific neurons in the NTS to interact with selected neuronal subsets in the DMV. In particular, we propose that neurons in the medial DMV receive a fast excitatory input from neurons in the cen-NTS (an interactions that could provide the anatomical substrate for the receptive relaxation reflex), while neurons in the lateral DMV receive a "slower or longer lasting inhibitory input from neurons in the com-NTS (an interaction that could play a role in the ileal brake phenomenon). Hypothesis 2: The medullary raphe nuclei integrate GI reflex activity by providing a selective modulation of NTS-DMV synapses. It is proposed that this modulation is accomplished by medullary raphe neurons that excite of subset of DMV neurons and/or inhibit a subpopulation of NTS neurons via the release of 5-HT, TRH and/or SP. The hypotheses will be tested using whole cell patch clamp recordings in brainstem slices that include the NTS, the DMV and the raphe nuclei. The slices will be taken from rats that have undergone placement of fluorescent tracers in isolated branches of the subdiaphragmatic vagus nerve or select regions of the GI tract. This protocol will label a subset of the terminals of visceral afferents that terminate on NTS neurons as well as the somata of DMV neurons that project to the region of the GI tract that received the injection of the fluorescent tracer. Synaptic currents and potentials will be evoked from the NTS and will be recorded in DMV and/or NTS; the modulation of the DMV-NTS synapses will be analyzed upon stimulation of the adjacent raphe medullary nuclei and upon perfusion with 5-HT, TRH and/or SP. Data obtained from pursuing these specific aims will reveal the synaptic currents underlying the behavior of discrete NTS and DMV neuronal populations. Furthermore, the fundamental circuitry of the vago-vagal reflex will be elucidated. These data will increase our understanding of how the interaction between NTS and DMV neurons can result in the pattern of neuronal activity controlling vago-vagal reflexes such as gastric receptive relaxation and ileal brake.