Neural Circuitry in the Dorsal Vagal Complex

描述(申请人提供)：背侧迷走神经复合体(DVC)中的神经元通讯对于整合内脏传入和其他输入，并通过迷走神经将整合的信号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因素。尽管这一回路在控制摄食和消化方面的重要性得到了公认，但人们对DVC中局部细胞的相互作用知之甚少。这一假设的基本假设是，迷走神经背核(DMV)中控制胃功能的神经元的活动主要受孤束核(NTS)神经元产生的抑制性GABA能输入的控制。NTS GABA神经元的活动受谷氨酸能兴奋性和GABA能抑制性突触输入的调节。我们认为GABA对节前迷走神经运动输出的控制是通过突触后GAAA受体介导的时相和紧张性抑制来完成的，DVC中特定的细胞相互作用的组织方式与在其他感觉-运动系统中很好地发展的概念一致，即局部抑制电路协调孤立复合体的功能区之间的反应。胃肠道和其他自主神经功能障碍会影响糖尿病患者，高血糖会显著改变中枢迷走神经运动功能。我们进一步提出，在1型糖尿病模型中，胃相关DMV神经元上GABAA受体介导的电流发生了功能性改变。我们将使用多学科方法来研究GABA介导的DVC神经元之间的突触传递，特别关注NTS中已识别的GABA能神经元的抑制性突触控制，以及胃肠道控制背景下DMV中的神经元。电生理实验将使用成熟雄性小鼠的脑切片标本进行体外实验，在这些切片中，DMV和NTS神经元可以通过它们与胃的解剖联系、它们的GABA含量或两者兼而有之来识别。通过全细胞膜片钳记录，我们将使用笼养谷氨酸的光激活来选择性地刺激局部神经元的胞体-树突区，以分析孤立复合体内GABA介导的连接。我们的目标是确定：1)紧张性GABA能电流对DMV神经元活动的贡献；2)NTS中已识别的胃相关GABA能神经元如何受到GABA输入的调节；以及3)高血糖对1型糖尿病模型中GABA电流的影响。我们将把电生理结果与药理学和分子生物学分析相关联，以构建局部GABA能控制DMV神经元活动的细胞模型。

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.