Regulation of extrasynaptic GABA-A receptors in health and disease

突触外 GABA-A 受体在健康和疾病中的调节

• 批准号: 9206085
• 负责人: Christopher Bruce Ransom
• 金额: --
• 依托单位: VA PUGET SOUND HEALTHCARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-10-01 至 2019-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9206085
• 关键词: Acute; Affect; Affinity; Agonist; Area; Biochemical; Biological Assay; Brain; Brain Injuries; Brain region; Cells; Chemicals; Chronic; Cyclic AMP-Dependent Protein Kinases; Data; Development; Disease; Dopamine D2 Receptor; Electric Stimulation; Epilepsy; G-Protein-Coupled Receptors; G-substrate; GABA Receptor; GABA-A Receptor; GTP-Binding Protein alpha Subunits, Gs; Health; Hippocampus (Brain); Individual; Ion Channel; Knowledge; Lead; Link; Measures; Mediating; Memory; Mental Depression; Middle East; Modeling; Mood Disorders; Mus; Neurologic Symptoms; Neurons; Neurophysiology - biologic function; Neurotransmitter Receptor; Neurotransmitters; Periodicity; Pharmacology; Phosphotransferases; Physiological; Procedures; Property; Protein Inhibition; Protein Kinase; Proteins; Receptor Activation; Recurrence; Regulation; Role; Signal Pathway; Signal Transduction; Site; Slice; Stroke; Surface; Synapses; Techniques; Testing; Traumatic Brain Injury; Veterans; Whole-Cell Recordings; aging population; controlled cortical impact; dentate gyrus; effective therapy; entorhinal cortex; falls; gamma-Aminobutyric Acid; granule cell; hippocampal pyramidal neuron; improved; inhibitor/antagonist; neuropsychiatry; postsynaptic; public health relevance; receptor; receptor function; relating to nervous system; therapeutic target; virtual

 DESCRIPTION (provided by applicant): The inhibitory neurotransmitter GABA activates several types of receptors that are therapeutic targets for the treatment of epilepsy and other neuropsychiatric illness. GABAA receptors are linked to a Cl ion channel and produce electrical signals when activated at synapses. GABAB receptors are G- protein coupled receptors (GPCRs) that regulate intracellular signaling pathways. In addition to synaptic GABAA receptors, there are unique GABAA receptors localized to extrasynaptic sites. These high-affinity extrasynaptic GABAA receptors are tonically activated by the low levels of ambient GABA in the brain. The tonic form of inhibition produced by extrasynaptic GABAA receptors importantly affects cellular and network excitability. Emerging data indicate that extrasynaptic GABAA receptors in several brain regions are regulated by postsynaptic GABAB receptors. Because the intracellular signaling pathways affected by GABAB receptors are shared by many GPCRs, other neurotransmitter receptors may also regulate extrasynaptic GABAA receptors. This proposal describes three hypotheses to investigate the regulation of extrasynaptic GABAA receptors in health and disease. It is hypothesized that multiple neurotransmitters acting through GPCRs regulate extrasynaptic GABA receptors. Tonic currents produced by extrasynaptic GABAA receptors will be recorded from dentate gyrus granule cells (DGGCs) and CA1 pyramidal neurons in acute hippocampal brain slices using standard whole cell techniques. The effects of intracellular signaling pathways on tonic currents will be investigated. Using selective agonists and antagonists, the effects of other GPCRs (i.e. ß- adrenoreceptors, D2 dopamine receptors, and 5-HT2 receptors) on tonic currents will be determined. It is predicted that tonic currents will be enhanced by PKA inhibition (D2 receptors) and PKC activation (5HT2 receptors). Activation of PKA by ß-adrenoreceptors is predicted to reduce tonic currents. Biochemical studies will be done to determine if intracellular signaling pathways enhance tonic currents by increasing surface expression of GABAA receptors. Spontaneous physiological or pathophysiological neural activity can produce periodic and transient increases in ambient GABA levels. It is hypothesized that periodic increases in ambient GABA will activate postsynaptic GABAB receptors and enhance extrasynaptic GABAA receptor function. Tonic currents will be repeatedly measured before and during procedures to periodically increase ambient GABA. Three approaches will be used to produce transient increases in ambient GABA; 1. periodic application of exogenous GABA, 2. stimulating release of endogenous GABA (electrical stimulation, high K+), and 3. inducing spontaneous interictal discharges with 4-AP. It will be confirmed that the effects of these procedures resulted from postsynaptic GABAB receptor activation using the GABAB receptor antagonist CGP55845 and pipette solutions containing a G protein inhibitor (GDP-ß-s). Traumatic brain injury (TBI) alters GABAA receptor function in the hippocampus. It is hypothesized that GPCRs regulate extrasynaptic GABAA receptors following experimental TBI. We will determine the effects of TBI on basal tonic currents and their regulation by GPCRs. Specifically, it is hypothesized that tonic currents of DGGCs will be enhanced by TBI, due in part to increased activation of GPCRs.

 描述（由申请人提供）： 抑制性神经递质 GABA 可激活多种类型的受体，这些受体是治疗癫痫和其他神经精神疾病的治疗靶点。 GABAA 受体与 Cl 离子通道相连，在突触激活时产生电信号。 GABAB 受体是调节细胞内信号传导途径的G 蛋白偶联受体(GPCR)。除了突触 GABAA 受体外，还有位于突触外位点的独特 GABAA 受体。这些高亲和力的突触外 GABAA 受体被大脑中低水平的环境 GABAA 激活。突触外 GABAA 受体产生的强直性抑制对细胞和网络的兴奋性有重要影响。 新数据表明，几个大脑区域的突触外 GABAA 受体受到突触后 GABAB 受体的调节。由于受 GABAB 受体影响的细胞内信号通路是许多 GPCR 所共有的，因此其他神经递质受体也可能调节突触外 GABAA 受体。该提案描述了三个假设来研究突触外 GABAA 受体在健康和疾病中的调节。 据推测，多种神经递质通过 GPCR 调节突触外 GABA 受体。使用标准全细胞技术，从急性海马脑切片中的齿状回颗粒细胞 (DGGC) 和 CA1 锥体神经元记录突触外 GABAA 受体产生的强直电流。将研究细胞内信号通路对强直电流的影响。使用选择性激动剂和拮抗剂，将确定其他 GPCR（即 β- 肾上腺素受体、D2 多巴胺受体和 5-HT2 受体）对强直电流的影响。预计PKA抑制会增强强直电流 （D2 受体）和 PKC 激活（5HT2 受体）。 β-肾上腺素受体激活 PKA 预计会减少强直电流。将进行生化研究以确定细胞内信号通路是否通过增加 GABAA 受体的表面表达来增强强直电流。 自发的生理或病理生理神经活动可导致环境 GABA 水平周期性和短暂性增加。据推测，环境 GABA 的周期性增加将激活突触后 GABAB 受体并增强突触外 GABAA 受体功能。在手术之前和过程中将重复测量强直电流，以定期增加环境 GABA。将使用三种方法来产生环境 GABA 的瞬时增加； 1. 定期应用外源性 GABA，2. 刺激内源性 GABA 的释放（电刺激，高 K+），以及 3. 用 4-AP 诱导自发性发作间期放电。将证实这些程序的效果是由使用 GABAB 受体拮抗剂 CGP55845 和含有 G 蛋白抑制剂 (GDP-ß-s) 的移液管溶液激活突触后 GABAB 受体引起的。 创伤性脑损伤（TBI）改变 GABAA 受体在海马体中发挥作用。据推测，GPCR 在实验性 TBI 后调节突触外 GABAA 受体。我们将确定 TBI 对基础强直电流的影响及其 GPCR 的调节。具体来说，假设 TBI 会增强 DGGC 的强直电流，部分原因是 GPCR 激活增加。