Glucocorticoids and endocannabinoids in vagal complex

描述（由申请人提供）：本研究资助提案中的实验将确定内源性大麻素（eCB）配体和迷走神经背侧运动核（DMV）中糖皮质激素诱导的eCB释放的细胞和突触效应。DMV中的神经元调节副交感神经输出到大部分脑下内脏，因此关键地控制进食、消化、葡萄糖和胰岛素分泌以及其他代谢功能。它们的活动在很大程度上受DMV的突触输入控制，DMV由局部释放的化学物质和循环激素调节。大麻素、香草素和糖皮质激素对DMV神经元的调节已经被提出;当集中应用这些化合物时，会深刻地改变副交感神经功能。几种eCB配体被认为是以逆行方式从细胞膜释放，激活大麻素1型受体（CB1R）和瞬时受体电位香草素1型（TRPV 1）。在DMV中，TRPV1的激活增强神经递质的释放，而CB1R倾向于抑制突触。这两种效应都是通过激活突触前末梢上的受体而发生的。初步证据表明，eCB配体从DMV神经元释放，糖皮质激素或去极化可以诱导这种释放。因此，DMV中的eCB活性可以调节TRPV1和CB1R活性。释放的eCB配体的类型、大多数eCB配体对突触活性的影响以及DMV中eCB释放的触发因素或机制都是未知的。我们将使用脑干切片中DMV神经元的全细胞膜片钳记录来确定eCB配体对DMV细胞活性的影响，并将使用药理学和生物化学方法确定该区域细胞释放的化合物。实验将由三个具体目标指导：1）区分eCB配体对DMV中CB1R和TRPV 1的作用; 2）确定eCB参与介导糖皮质激素对DMV中局部回路的快速作用;和3）鉴定糖皮质激素作用的细胞途径。我们将测试的假设，eCB改变TRPV1和CBR1在DMV的活动在特定的和可预测的空间，时间，功能相关，和活动依赖性模式，糖皮质激素诱导eCB释放DMV细胞通过作用于膜结合G蛋白偶联受体DMV神经元。正在研究基于eCB系统的药物在各种神经系统病理学中的治疗用途，包括与进食、消化和肥胖相关的疾病。在某些系统中释放eCB的糖皮质激素被广泛使用，并且也通过压力刺激释放。这些研究的结果对于预测和理解这些化合物如何相互作用并影响副交感神经功能至关重要。由于在糖皮质激素升高患者的迷走神经系统中控制eCB水平的益处，也存在可能的转化益处。内源性大麻素化合物在负责维持器官系统功能的脑干区域中具有特别复杂的作用，并且正在开发基于改变大脑中这些化合物的许多药物疗法，而不知道它们在这个关键大脑区域中的作用。这项研究拨款提案中的实验将确定这些药物的特性，它们如何被糖皮质激素释放，以及它们对神经元的作用。这些研究的结果对于预测和理解这些化合物如何相互作用以影响消化功能至关重要，它们也将适用于多种其他神经系统。

DESCRIPTION (provided by applicant): The experiments in this research grant proposal will identify the cellular and synaptic effects of endogenous cannabinoid (eCB) ligands and of glucocorticoid-induced release of eCBs in the dorsal motor nucleus of the vagus (DMV). Neurons in the DMV regulate parasympathetic output to most of the subdiaphragmatic viscera and therefore critically control feeding, digestion, glucose and insulin secretion, and other metabolic functions. Their activity is largely controlled by synaptic input to the DMV, which is modulated by locally released chemicals and circulating hormones. Regulation of DMV neurons by cannabinoids, vanilloids, and glucocorticoids has been suggested; when applied centrally these compounds profoundly alter parasympathetic function. Several eCB ligands, which are thought to be released from cell membranes in a retrograde fashion, activate both cannabinoid type 1 receptors (CB1R) and transient receptor potential vanilloid type 1 (TRPV1). In the DMV, activation of TRPV1 enhances neurotransmitter release, whereas CB1R tends to inhibit synapses. Both effects occur by activation of receptors on presynaptic terminals. Preliminary evidence suggests that eCB ligands are released from DMV neurons, and that glucocorticoids or depolarization can induce this release. Thus, eCB activity in the DMV may modulate both TRPV1 and CB1R activity. Neither the type(s) of eCB ligands released, the effects of most eCB ligands on synaptic activity, nor the trigger or mechanism of eCB release in the DMV are known. We will use whole-cell patch-clamp recordings from DMV neurons in brainstem slices to identify effects of eCB ligands on cellular activity in the DMV, and will also identify the compounds released by cells in the area using pharmacological and biochemical methods. The experiments will be guided by three specific aims: 1) Differentiate effects of eCB ligands on CB1R and TRPV1 in the DMV; 2) Determine the eCB involvement in mediating rapid effects of glucocorticoids on local circuitry in the DMV; and 3) Identify the cellular pathway of the glucocorticoid effect. We will test the hypotheses that eCBs alter TRPV1 and CBR1 activity in the DMV in specific and predictable spatial, temporal, functionally relevant, and activity-dependent patterns, and that glucocorticoids induce eCB release from DMV cells by acting at membrane-bound G protein-coupled receptors on DMV neurons. Drugs based on the eCB system are being investigated for therapeutic use in a variety of nervous system pathologies, including disorders related to feeding, digestion, and obesity. Glucocorticoids, which release eCBs in some systems, are widely prescribed, and are also released by stressful stimuli. Results of these studies will be critical to predicting and understanding how these compounds interact with each other and affect parasympathetic function. Possible translational benefits also exist because of the benefit in controlling eCB levels in the vagal system of patients with elevated glucocorticoids. PUBLIC HEALTH RELEVANCE Endogenous cannabinoid compounds have particularly complex actions in the area of the brainstem most responsible for maintaining functions of organ systems, and a number of drugs therapies based on altering these compounds in the brain are being developed without knowledge about their effects in this critical brain area. The experiments in this research grant proposal will identify the characteristics of these drugs, how they are released by glucocorticoid hormones, and what actions they have on the neurons. Results of these studies will be critical for predicting and understanding how these compounds interact to affect digestive functions, and they will also be applicable to multiple other neuronal systems.