Mechanisms of Ligand-Induced GABA Receptor Plasticity

配体诱导 GABA 受体可塑性的机制

• 批准号: 6946683
• 负责人: RICHARD W OLSEN
• 金额: $ 22.6万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6946683
• 关键词: GABA receptor; benzodiazepines; biotin; cerebellum; drug tolerance; drug withdrawal; ethanol; gamma aminobutyrate; hippocampus; laboratory mouse; laboratory rat; neural plasticity; neurophysiology; protein localization; protein structure function; receptor binding; steroids; tissue /cell culture

The objectives of this component are to analyze the molecular mechanisms of chronic GABAergic ligand-induced plasticity in the central nervous system (CNS). Various plasticity-inducing treatments produce changes in levels of the GABAA receptor (GABAR) subunit alpha4 and its associated partners, gamma2 or 8, accompanied by altered sensitivity to endogenous neurosteroids. In this program, we have determined that alpha4beta3delta subunit-containing GABAR are extrasynaptically localized, involved in tonic inhibition, and the major target of modulation of CNS excitability by neurosteroids and anesthetics including ethanol, while being insensitive to benzodiazepines. In particular we showed by several lines of evidence that the alpha6beta3delta subtype of GABAR is very likely the target of action of ethanol in the cerebellum. This important discovery needs substantiation and forms the rationale for Aim I. We suggest that the alpha4/6beta3delta GABAR are both susceptible to plasticity and positioned to regulate excitability via neurosteroid-modulated tonic inhibition. In this project Aim II we will compare and contrast changes in GABAR following chronic steroid (extrasynaptic delta subunit-containing target) and chronic BZ (synaptic gamma2 subunit-containing target). In drug-treated mice, we will measure biochemically the levels of GABAR subunits in hippocampus and cerebellum and partnering of subunits using antibodies, as well as binding assays for GABAR levels and allosteric modulation indicative of subunit switches. In drug-treated primary cultured hippocampal neurons, we will measure the content of cell surface GABAR subunits and subunit partners using biotinylation. Plastic changes following chronic GABAergic drugs are relevant not only to the development of tolerance to clinically useful agents like benzodiazepines (BZ) as well as withdrawal and dependence, but also to the control of excitability by the GABA system. This in turn is critically important to normal CNS information processing and changes that occur in response to usual or unusual experiences (plasticity), including epileptogenic phenomena.

本部分的目的是分析慢性GABA能配体诱导的中枢神经系统（CNS）可塑性的分子机制。各种可塑性诱导处理产生GABAA受体（GABAR）亚单位α 4及其相关配偶体γ 2或γ 8水平的变化，伴随着对GABAA受体（GABAR）亚单位α 4和γ 2或γ 8的敏感性改变。 内源性神经类固醇在这个程序中，我们已经确定，α 4 β 3 δ亚基含有GABAR的突触外本地化，参与紧张性抑制，和中枢神经系统兴奋性的神经类固醇和麻醉剂，包括乙醇调制的主要目标，而苯二氮卓类不敏感。特别是，我们通过几条证据表明，GABAR的α 6 β 3 δ亚型很可能是乙醇在小脑中作用的靶点。这一重要发现需要得到证实，并构成了目标I的理论基础。我们认为，α 4/6 β 3 δ GABAR既易受可塑性的影响，又可通过神经类固醇调节的紧张性抑制来调节兴奋性。在这个项目的目的II中，我们将比较和对比GABAR的变化后，慢性类固醇（突触外δ亚单位含有目标）和慢性BZ（突触γ 2亚单位含有目标）。在药物治疗的小鼠中，我们将用生物化学方法测量海马和小脑中GABAR亚基的水平，并使用抗体进行亚基的配对，以及GABAR水平和指示亚基开关的变构调节的结合测定。在药物处理的原代培养海马神经元中，我们将测量细胞表面GABAR的含量， 亚基和亚基配偶体。长期服用GABA能药物后的可塑性变化不仅与对临床有用药物（如苯二氮卓类（BZ））的耐受性以及戒断和依赖性的发展有关，而且与GABA系统对兴奋性的控制有关。这反过来又是至关重要的正常中枢神经系统的信息处理和变化，发生在响应通常或不寻常的经验（可塑性），包括癫痫现象。