Depolarization-Secretion Coupling in Nerve Terminals

神经末梢的去极化-分泌耦合

• 批准号: 6870417
• 负责人: JOSE R LEMOS
• 金额: $ 37.46万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-05-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6870417
• 关键词: action potentials; adenosine; adenosine triphosphate; calcium channel; calcium flux; electrophysiology; high performance liquid chromatography; hormone regulation /control mechanism; hydrolysis; hypothalamus; immunocytochemistry; laboratory rat; male; membrane activity; nerve endings; neurohypophysis; neuropeptides; neurotransmitter transport; oxytocin; purinergic receptor; purines; secretion; vasopressins

DESCRIPTION (provided by applicant): Although there is considerable evidence that the electrical activity of neuronal somata leads to the entry of Ca2+ and to the subsequent secretion of transmitters (i.e., Depolarization-secretion coupling), the molecular details of how ionic currents control the release of specific neuroactive substances from nerve terminals remain undetermined. Vasopressin (AVP) and oxytocin (OT) are synthesized by magnocellular neurons (MCN) of the hypothalamus and secreted from neurohypophysial (NH) terminals. OT neurons are characterized by a high frequency discharge during suckling which leads to the pulsatile release of OT. AVP neurons are characterized by their asynchronous phasic activity (bursting) during maintained AVP release. In both cases, it is the clustering, albeit with different time courses for each peptide, of spikes, which facilitates hormone release. We have discovered that there are different Calcium-channel subtypes in AVP vs. OT terminals, but that their biophysical properties cannot explain this differential facilitation of release. Therefore, we hypothesize that autocrine/paracrine feedback effects determine efficacy of bursting patterns of electrical activity to facilitate release of AVP vs. OT. ATP is thought to be co-released with the HNS peptides. Purines, such as ATP and adenosine, interact with specific receptors on neurons and glia, leading to a variety of effects. It is not known, however, whether these effects are at somata and/or synapses in the central nervous system (CNS). We have characterized the electrical and secretory effects on the HNS by exogenous purines, including effects on membrane ionic conductances in these CNS neurons vs. their nerve terminals. The HNS affords the unique opportunity of unraveling the complicated effects of endogenous purines in the CNS by comparing such effects on different neuronal compartments. Our goal is to determine membrane mechanisms that mediate endogenous purinergic- induced modifications of neurohormone secretion during physiological patterns of electrical stimulation. To achieve these objectives, perforated-patch recordings of Ca2+ and K+ currents will be made from identified, isolated nerve terminals and somata of the HNS. Effects on release will be compared between the intact HNS and NH terminals by the use of ELISAs and capacitance measurements. Loose patch-clamp recordings from nerve terminals and somata in the intact HNS will allow analysis of how bursting activity regulates peptide release in the complete system. These studies will provide a unique opportunity to determine if endogenous purinergic feedback regulation occurs at the terminals of CNS neurons.

描述（由申请人提供）：尽管有大量证据表明，神经元的somata的电活动导致Ca2+的进入以及随后的发射器分泌（即去极化分泌偶联），但离子电流如何控制特定神经活动的分子细节，这些细节仍在杂种终止中释放出来。血管加压素（AVP）和催产素（OT）由下丘脑的巨细胞神经元（MCN）合成，并从神经型（NH）末端分泌。 OT神经元的特征是哺乳过程中高频排出，这导致OT的脉冲释放。 AVP神经元的特征是它们在维持的AVP释放过程中的异步阶段活性（爆发）。在这两种情况下，尽管有不同的时间课程，但每个肽的尖峰都有不同的时间课程，这促进了激素释放。我们发现，AVP与OT终端中有不同的钙通道亚型，但是它们的生物物理性能无法解释这种释放的差异促进。因此，我们假设自分泌/旁分泌反馈效应决定了电活动的爆发模式的功效，以促进AVP与OT的释放。 ATP被认为与HNS肽共同发行。嘌呤（例如ATP和腺苷）与神经元和神经胶质的特定受体相互作用，从而产生各种作用。但是，这些影响是否在somata和/或中枢神经系统（CNS）中的突触尚不清楚。我们已经通过外源性嘌呤对HNS的电和分泌作用进行了表征，包括对这些CNS神经元与神经末端中膜离子电导的影响。 HNS提供了通过比较对不同神经元隔室的这种影响来揭示内源性嘌呤在中枢神经系统中复杂作用的独特机会。我们的目标是确定介导内源性嘌呤能诱导的在电刺激生理模式中神经激素分泌的修饰的膜机制。为了实现这些目标，Ca2+和K+电流的穿孔斑点记录将由识别的，孤立的神经末端和HNS的somata进行。通过使用ELISA和电容测量，将比较完整的HN和NH终端之间对释放的影响。完整的HNS中神经终端和SOMATA的斑块钳记录将允许分析爆发活动如何调节完整系统中的肽释放。这些研究将提供一个独特的机会来确定内源性嘌呤能反馈调节是否发生在CNS神经元的末端。