Activity of brainstem neurons

描述(申请人提供)：随着高效“可卡因”和“游离碱”的引入，可卡因滥用在20世纪80年代的S和90年代的S急剧增加，是滥用的主要毒品。流行病学数据表明，根据药物使用和事件发生之间的时间关系，可卡因是吸毒者心肌梗死、中风、血栓形成、高血压和心律失常的一个促成因素。临床和动物研究表明，中枢交感神经系统在可卡因诱导的心血管异常中起关键作用。这一假设的核心假设是可卡因与位于延髓头端腹外侧区(RVLM)神经元中的Sigma-1受体相互作用，导致谷氨酸能反应增强，从而增强可卡因使用者的交感神经活动。有证据表明，可卡因的中枢作用是通过Sigma-1受体介导的。本项目的目的是明确可卡因对大鼠RVLM神经元的心血管中枢作用，特别是对Sigma-1受体的影响。首先，免疫组织化学研究将检查Sigma-1受体的表达及其与球突投射RVLM神经元的谷氨酸受体亚型的关系。其次，将被微量注射到RVLM区的可卡因对乌拉坦麻醉大鼠的血压、心率和更大的内脏神经活动的影响将被评估。此外，在使用Sigma-1受体拮抗剂或多巴胺和去甲肾上腺素摄取抑制剂预处理前后，将监测可卡因对升压反应的影响。第三，用Fura-2方法测定Sigma-1受体拮抗剂处理前后分离的逆行标记的RVLM神经元对谷氨酸和可卡因的反应中的细胞内钙离子浓度。第四，对逆行标记的RVLM神经元进行全细胞贴片记录，研究可卡因对单个神经元电活动和突触传递的影响。总的来说，这些研究旨在提供一种机械方法，以了解可卡因与心血管活动相关的中心作用。可卡因滥用是多种心血管疾病的危险因素。能够识别对可卡因有反应的受体和递质，将是更好地理解可卡因引起的心脏疾病机制的重要一步。更重要的是，所获得的知识将允许理性地设计新的治疗药物，例如Sigma-1受体或谷氨酸受体拮抗剂的亚型，用于治疗可卡因引起的心血管功能障碍。

DESCRIPTION (provided by applicant): With the introduction of high potency "crack" and "freebase", cocaine abuse increased dramatically in the 1980's and 1990's, and is the leading drug of abuse. Epidemiological data have implicated cocaine as a contributing factor to myocardial infarction, stroke, thrombosis, hypertension and arrhythmias in users on the basis of temporal relationship between drug use and event onset. Clinical and animal studies suggest that the central sympathetic nervous system plays a critical role in cocaine-induced cardiovascular abnormality. The hypothesis central to this proposal is that cocaine interacts with sigma-1 receptors located in neurons of the rostral ventrolateral medulla (RVLM), leading to a potentiation of glutamatergic responses, thereby an augmented sympathetic nerve activity in cocaine users. There is evidence that the central action of cocaine is mediated through sigma-1 receptors. The goal of this project is to define the central cardiovascular action of cocaine on RVLM neurons of the rat, with particular reference to sigma-1 receptors. First, immunohisto- chemical studies will examine the expression of sigma-1 receptors and their relationship to subtypes of glutamate receptors in a population of bulbospinally projecting RVLM neurons. Second, the effect of cocaine, which will be microinjected into the RVLM area, on blood pressure, heart rate and greater splanchnic nerve activity will be assessed in urethane-anesthetized rats. In addition, the effect of cocaine on the pressor response will be monitored before and after pretreatment with sigma-1 receptor antagonists or dopamine and norepinephrine uptake inhibitors. Third, intracellular Ca2+ concentrations in dissociated, retrogradely labeled RVLM neurons in response to glutamate and cocaine before and after treatment of sigma-1 receptor antagonists will be measured by means of the Fura 2 method. Fourth, whole-cell patch recordings will be made from retrogradely labeled RVLM neurons in the coronal medullary slice and the effect of cocaine on the electrical activity and synaptic transmission of single neurons will be studied. Collectively, these studies are designed to provide a mechanistic approach to the understanding of the central action of cocaine relative to cardiovascular activity. Cocaine abuse is a risk factor to a variety of cardiovascular disorders. To be able to identify the receptor and transmitters that respond to cocaine will be a major step toward a better understanding of the mechanisms involved in cocaine-induced cardiac disorders. More importantly, the knowledge gained would permit a rational approach to the design of novel therapeutic agents, for example, sigma-1 receptor or subtypes of glutamate receptor antagonists, for the management of cocaine-induced cardiovascular dysfunction.