Neural circuitry in the dorsal vagal complex

描述（由申请人提供）：背侧迷走神经复合体（DVC）中的神经元通信对于整合内脏传入和其他输入以及将整合的信号通过迷走神经转化为协调的副交感运动输出至关重要。特别是，GABA能抑制是该区域神经元功能的主要调节剂。尽管公认的重要性，这一电路在控制喂养和消化，相对知之甚少的DVC中的局部细胞相互作用。该提议的一般假设是，控制胃功能的迷走神经背侧运动核（DMV）中的神经元的活动显著地由来自孤束核（NTS）中的神经元的抑制性GABA能输入控制。孤束核GABA能神经元的活动受兴奋性和抑制性突触输入的共同调节。我们建议，GABA能控制节前迷走神经运动输出是通过阶段性和紧张性突触后GABAA受体介导的抑制和特定的细胞相互作用在DVC组织的方式，符合的概念，以及在其他感觉运动系统，局部抑制电路协调孤立复杂的功能区之间的反应。胃肠和其他自主神经功能障碍影响糖尿病患者，高血糖显著改变中枢迷走神经运动功能。我们进一步提出，GABAA受体介导的电流在胃相关的DMV神经元功能改变1型糖尿病模型。我们将使用多学科的方法来研究GABA介导的突触传递的神经元之间的DVC，特别是集中在抑制性突触控制确定的GABA能神经元的NTS，以及在DMV的神经元在胃肠道控制的背景下。将使用来自成熟雄性小鼠的脑切片制备物在体外进行电生理学实验，其中DMV和NTS神经元可通过其与胃的解剖学连接、其GABA含量或两者来鉴定。与全细胞膜片钳记录，我们将使用光激活的笼状谷氨酸选择性地刺激局部神经元的胞体树突状区域，以分析GABA介导的连接内的孤立复合体。我们的目标是确定：1）紧张性GABA能电流对DMV中神经元活动的贡献; 2）NTS中识别的胃相关GABA能神经元如何受GABA输入调节;和3）1型糖尿病模型中高血糖对GABA电流的影响。我们将电生理结果与药理学和分子生物学分析相关联，以构建DMV神经元活动的局部GABA能控制的细胞模型。公共卫生相关性：调节胃肠道系统的神经元之间的抑制性连接对进食和消化至关重要，但它们如何控制胃的输出在很大程度上是未知的。我们已经发现了一种迄今为止尚未研究的强大的调节大脑如何控制肠道的方法的证据，并且这种机制在1型糖尿病模型中发生了改变。这里的实验将检查控制肠道相关的神经元活动的突触机制，并将指出新的方式修改活动的胃肠道系统响应特定的触发与喂养和代谢失调的病理条件下。

DESCRIPTION (provided by applicant): Neuronal communication in the dorsal vagal complex (DVC) is critical for integrating visceral afferent and other inputs, and translating that integrated signal into a coordinated parasympathetic motor output via the vagus nerve. In particular, GABAergic inhibition is a dominant regulator of neuronal function in the area. Despite the recognized importance of this circuitry in controlling feeding and digestion, relatively little is known about local cellular interactions in the DVC. The general hypothesis of this proposal is that activity of neurons in the dorsal motor nucleus of the vagus (DMV) that control gastric function is prominently controlled by inhibitory GABAergic inputs arising from neurons in the nucleus tractus solitarius (NTS). The activity of NTS GABA neurons is regulated by both glutamatergic excitatory and GABAergic inhibitory synaptic inputs. We propose that GABAergic control of preganglionic vagal motor output is accomplished by both phasic and tonic postsynaptic GABAA receptor-mediated inhibition and that specific cellular interactions in the DVC are organized in a manner that consistent with the concept, well developed in other sensory-motor systems, that local inhibitory circuitry coordinates responses between functional areas of the solitary complex. Gastrointestinal and other autonomic dysfunction affects people with diabetes mellitus and hyperglycemia significantly alters central vagal motor function. We further propose that GABAA receptor-mediated currents in gastric-related DMV neurons are functionally altered in a model of type 1 diabetes mellitus. We will use a multidisciplinary approach to examine GABA-mediated synaptic transmission between neurons in the DVC, focusing particularly on inhibitory synaptic control of identified GABAergic neurons in the NTS, as well as on neurons in the DMV in the context of gastrointestinal control. Electrophysiological experiments will be done in vitro using brain slice preparations from mature male mice in which DMV and NTS neurons can be identified by their anatomical connection with the stomach, their GABA content, or both. With whole-cell patch-clamp recordings, we will use photoactivation of caged glutamate to stimulate selectively the soma-dendritic regions of local neurons in order to analyze GABA-mediated connections within the solitary complex. We aim to determine: 1) the contribution of tonic GABAergic currents to neuronal activity in the DMV; 2) how identified gastric-related GABAergic neurons in the NTS are regulated by GABA input; and 3) effects of hyperglycemia on GABA currents in a model of type 1 diabetes. We will correlate electrophysiological results with pharmacological and molecular biological analyses to construct a cellular model of local GABAergic control of DMV neuron activity. PUBLIC HEALTH RELEVANCE: Inhibitory connections between neurons that regulate the gastrointestinal system are critical to feeding and digestion, but how they control output to the stomach is largely unknown. We have uncovered evidence of a heretofore unstudied and powerful means of regulating how the brain controls the gut, and that this mechanism is altered in a model of type 1 diabetes mellitus. The experiments here will examine the synaptic mechanisms controlling gut-related neuron activity and will point to new ways of modifying activity of the gastrointestinal system in response to specific triggers associated with feeding and under pathological conditions of metabolic dysregulation.