OPIOID ACTION IN HIPPOCAMPUS

海马体中的阿片类药物作用

基本信息

批准号：
2120215
负责人：
Carl R. Lupica
金额：
$ 8.81万
依托单位：
UNIVERSITY OF COLORADO DENVER
依托单位国家：
美国
项目类别：
财政年份：
1992
资助国家：
美国
起止时间：
1992-07-01 至 1995-06-30
项目状态：
已结题

项目摘要

Opioids have been demonstrated to have actions on many neurons of the central nervous system. However, their functional role(s) as neurotransmitters or neuromodulators in the mammalian brain remains poorly understood. The following experiments will evaluate the actions of opioids, acting at pharmacologically defined receptor subtypes, as neuromodulators of synaptic transmission in the CA1 region of the hippocampus; an area of the brain possessing low concentrations of endogenous enkephalin peptides but moderate to high concentrations mu and delta opioid receptors. These experiments will utilize extracellular and intracellular electrophysiological techniques to describe the effects of opioids on synaptic transmission and on individual neurons in brain slice preparations. The first set of experiments will focus on determining the source and locations of the substrates upon which mu and delta opioid receptor agonists act to increase synaptic excitability in the CA1 region of the hippocampus. In particular, these experiments will utilize extracellular, whole-cell, and conventional intracellular recordings to determine the mechanisms by which mu and delta opioids act to increase population spikes and intracellular EPSPs recorded from CA1 pyramidal neurons. The second set of experiments will determine the receptor selectivity of opioid actions on CAI pyramidal cells, the relative locations of mu and delta opioid receptors in the hippocampal slice, and the actions of mu and delta opioids on subpopulations of CAl interneurons. The third set of experiments will utilize various strategies to determine the possible cellular mechanisms by which mu and delta opioids act upon hippocampal interneurons, and whether this action is exercised upon interneuron nerve terminals or somata. We will do this, first, by attempting to block enkephalin effects with potassium channel antagonists while recording from pyramidal neurons or interneurons. Next, we will examine the effects of selective mu and delta opioids on hippocampal interneuron voltage-sensitive calcium responses. To more directly assess the site of opioid action, we will measure GABA release from hippocampal slices while superfusing selective mu or delta enkephalins in the presence and absence of tetrodotoxin, and we will characterize these selective enkephalin effects on interneurons and pyramidal neurons, simultaneously, using paired intracellular recordings. The investigations described in this grant proposal should improve our understanding of the specific receptor subtypes that opioids act upon, the cellular mechanisms mediating these responses, the roles opioids may play as neuromodulators in the hippocampus, and the diversity of cellular, mechanisms by which opioids control hippocampal output. In addition, since limbic structures like the hippocampus have been shown to participate in normal and abnormal behavioral states such as learning, epilepsy, and emotional behavior, these studies may yield new insights as to the interaction between opioids and these phenomena.

阿片类药物已被证明对许多神经元有作用中枢神经系统。然而，他们的职能角色是哺乳动物大脑中的神经递质或神经调节剂仍然存在不太了解。以下实验将评估这些行动阿片类药物，作用于药理学定义的受体亚型，如 CA1区突触传递的神经调节剂海马体；大脑中含有低浓度物质的区域内源性脑啡肽，但中至高浓度 mu 和 δ阿片受体。这些实验将利用细胞外和细胞内电生理技术来描述的影响阿片类药物对突触传递和脑切片中单个神经元的影响准备工作。第一组实验将集中于确定 mu 和 delta 阿片类物质的来源和位置受体激动剂可增加 CA1 区域的突触兴奋性海马体。特别是，这些实验将利用细胞外、全细胞和传统的细胞内记录确定 mu 和 delta 阿片类药物增加的机制从 CA1 锥体记录的群体峰值和细胞内 EPSP 神经元。第二组实验将确定受体阿片类药物对 CAI 锥体细胞作用的选择性，相对海马切片中 mu 和 delta 阿片受体的位置，以及 mu 和 delta 阿片类药物对 CA1 亚群的作用中间神经元。第三组实验将利用各种确定 mu 和可能的细胞机制的策略 δ阿片类药物作用于海马中间神经元，以及这种作用是否对中间神经元神经末梢或体细胞进行锻炼。我们会做首先，尝试用钾阻断脑啡肽的作用通道拮抗剂，同时从锥体神经元记录或中间神经元。接下来，我们将检查选择性 mu 和 δ阿片类药物对海马中间神经元电压敏感钙的影响回应。为了更直接地评估阿片类药物的作用部位，我们将测量海马切片中 GABA 的释放，同时选择性地进行超融合 mu 或 delta 脑啡肽在存在和不存在河豚毒素的情况下，以及我们将描述这些选择性脑啡肽对中间神经元的影响和锥体神经元，同时使用成对的细胞内录音。本拨款提案中描述的调查应提高我们对阿片类药物的特定受体亚型的了解作用、介导这些反应的细胞机制、作用阿片类药物可能在海马体中发挥神经调节剂的作用，并且其多样性阿片类药物控制海马输出的细胞机制。在此外，由于海马体等边缘结构已被证明参与正常和异常的行为状态，例如学习、癫痫和情绪行为，这些研究可能会产生新的见解：阿片类药物与这些现象之间的相互作用。