Chemical Anatomy and Synaptology of Vestibulo-Sympathetic Pathways

描述(由申请人提供)：前庭系统和血压控制之间的功能联系的存在已经被知道了近一个世纪。目前认为，动脉压力感受器参与调节回路，通过压力反射维持交感神经张力，而来自前庭末端器官的信号驱动更快的机制，抵消姿势变化的影响。后者通常被称为前庭交感神经反射(VSR)。该通路的初级传入终止于尾侧前庭核复合体(VNCc)中的细胞。这些二级神经元依次投射到参与心血管调节的脑干部位，如吻侧和尾侧延髓腹外侧区(分别为RVLm和CVLm)。RVLM中的细胞被认为是将前庭输入与压力感受器和其他感觉传入相结合，并向脊髓中间外侧细胞柱的节前交感神经元发送兴奋性投射。虽然这些交感前血管运动RVLM细胞的主要神经递质可能是谷氨酸，但许多神经活性分子已在这些细胞中共定位，包括C1细胞组儿茶酚胺。此外，球脊髓血管运动RVLM细胞接受来自CVLM的单突触GABA能投射，这对RVLM神经元产生强的抑制作用。因此，CVLM细胞可以看作是血管运动通路中的交感神经抑制中间神经元。我们研究计划的长期目标是确定参与前庭自主神经投射的神经递质、受体和信号通路，以便药物疗法可以针对它们来改善前庭自主神经障碍。本研究项目的具体目标是确定有助于血压调节的前庭通路的结构和化学解剖。该项目有两个目标，将以大鼠为实验模型，双侧正弦前庭电刺激激活前庭核团，遥测血压，顺行和逆行追踪，以及免疫荧光检测即刻早期基因蛋白产物c-Fos以及通路特异性神经递质和调节剂。目的1鉴定室旁核前庭神经元的敏感性、形态学、细胞学、神经递质(S)和调节剂(S)。这一目标将检验VSR通路的VNCc细胞具有不同于其他VNCc神经元和压力感受性反射通路的形态、生物学和/或化学解剖表型的总体假设。目的2确定前庭-交感轴突的神经支配模式(S)、突触类型和突触后伙伴。这一目标将通过确定前庭对交感前血管运动回路的输入的神经元和突触的特异性来解决我们的总体假设。这些假说是我们长期目标的基础，因为VSR途径在形态上或化学解剖学上与压力感受性反射途径分离的区域或细胞是对VSR进行特定药物干预的候选部位。

DESCRIPTION (provided by applicant): The existence of a functional link between the vestibular system and blood pressure control has been known for nearly a century. It is currently thought that arterial baroreceptors participate in a regulatory circuit that maintains sympathetic tone through the baroreflex while signals from the vestibular end organs drive a faster mechanism that counteracts the effects of a change in posture. This latter circuit is often called the vestibulo-sympathetic reflex (VSR). Primary afferents of this pathway terminate on cells in the caudal vestibular nuclear complex (VNCc). These second order neurons, in turn, project to brainstem sites involved in cardiovascular regulation such as the rostral and caudal ventrolateral medullary regions (RVLM and CVLM, respectively). Cells in the RVLM are thought to integrate the vestibular input with baroreceptor and other sensory afferents and send excitatory projections to preganglionic sympathetic neurons in the intermediolateral cell column of the spinal cord. While the principal neurotransmitter of these presympathetic vasomotor RVLM cells is likely to be glutamate, numerous neuroactive molecules have been co-localized in these cells, including catecholamines of the C1 cell group. In addition, bulbospinal vasomotor RVLM cells receive monosynaptic GABAergic projections from the CVLM, which tonically inhibit the RVLM neurons. As a result, CVLM cells can be viewed as sympathoinhibitory interneurons in the vasomotor pathway. The long-term goal of our research program is to identify the neurotransmitters, receptors, and signaling pathways that participate in vestibulo- autonomic projections so they can be targeted specifically by pharmacotherapeutics to ameliorate vestibulo- autonomic disorders. The specific objective of this research project is to identify the structural and chemical anatomy of vestibular pathways that contribute to blood pressure regulation. The project has two aims that will be pursued using rats as the experimental model, bilateral sinusoidal galvanic vestibular stimulation to activate the vestibular nuclei, telemetric detection of blood pressure, anterograde and retrograde tract-tracing, and immunofluorescence detection of the immediate early gene protein product c-Fos together with pathway- specific neurotransmitters and modulators. Aim 1 will identify the sensitivity, topography, cytology, neurotransmitter(s), and modulator(s) of vestibular neurons of the VSR. This aim will test the overall hypothesis that VNCc cells of the VSR pathway have a morphological, hodological and/or chemoanatomical phenotype that is distinct from other VNCc neurons and the baroreflex pathway. Aim 2 will identify the innervation pattern(s), synaptology and postsynaptic partners of vestibulo-sympathetic axons in RVLM and CVLM. This aim will address our over-arching hypothesis by determining the neuronal and synaptic specificity of vestibular input to pre-sympathetic vasomotor circuitry. These hypotheses are fundamental to our long-term goal, since regions or cells where the VSR pathway is morphologically or chemoanatomically segregated from the baroreflex pathway are candidate sites for specific pharmacological intervention into the VSR.