Activity of brainstem neurons

描述（由申请人提供）：随着强效“快克”和“freebase”的引入，可卡因的滥用在20世纪80年代和90年代急剧增加，是滥用的主要毒品。流行病学数据显示，根据药物使用与事件发生之间的时间关系，可卡因是导致使用者心肌梗死、中风、血栓形成、高血压和心律失常的一个因素。临床和动物研究表明，中枢交感神经系统在可卡因引起的心血管异常中起关键作用。该建议的核心假设是可卡因与位于延髓吻侧腹外侧（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。该项目的目标是确定可卡因对大鼠RVLM神经元的中枢心血管作用，特别是参考sigma-1受体。首先，免疫组化研究将在球脊髓突起的RVLM神经元中检测sigma-1受体的表达及其与谷氨酸受体亚型的关系。其次，将可卡因微注射到RVLM区域，评估其对尿素麻醉大鼠的血压、心率和更大的内脏神经活动的影响。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，将监测可卡因对加压反应的影响。第三，在sigma-1受体拮抗剂治疗前后，解离的逆行标记的RVLM神经元对谷氨酸和可卡因的反应中，细胞内Ca2+浓度将通过Fura 2方法测量。第四，对冠状髓片逆行标记的RVLM神经元进行全细胞膜片记录，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制方法来理解可卡因相对于心血管活动的中心作用。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朝着更好地理解可卡因引起的心脏疾病的机制迈出的重要一步。更重要的是，所获得的知识将允许合理的方法来设计新的治疗药物，例如，sigma-1受体或谷氨酸受体拮抗剂亚型，用于管理可卡因诱导的心血管功能障碍。

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.