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激活了几种类型的受体，这些受体是治疗癫痫和其他神经精神疾病的治疗靶标。 GABAA受体与Cl离子通道有关，并在突触处激活时产生电信号。 GABAB受体是调节细胞内信号通路的G蛋白偶联受体（GPCR）。除了合成的GABAA受体外，还有独特的GABAA受体，位于外交部位。这些高亲和力的突触外GABAA受体通常被大脑中的环境GABA含量低。外突触GABAA受体产生的抑制作用的补品形式重要地影响了细胞和网络令人兴奋。新兴数据表明，几个大脑区域的突触外GABAA受体受到突触后GABAB受体的调节。由于许多GPCR共享受GABAB受体影响的细胞内信号传导途径，因此其他神经递质受体也可能调节外突触外GABAA受体。该提案描述了三个假设，以调查健康和疾病中肌外GABAA受体的调节。假设通过GPCR作用的多个神经递质调节外突触GABA受体。通过标准的全细胞技术，将记录由牙齿回和颗粒细胞（DGGC）和CA1锥体神经元记录的刺激性GABAA受体产生的滋补电流。细胞内信号通路对补品电流的影响。使用选择性激动剂和拮抗剂，将确定其他GPCR（即ß-肾上腺素受体，D2多巴胺受体和5-HT2受体）对滋补电流的影响。预测PKA抑制作用会增强补品电流 （D2受体）和PKC激活（5HT2受体）。预测通过β-肾上腺肾上腺受体激活将减少滋补流。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滋补电流。自发的生理或病理生理神经活动可以在环境GABA水平上产生周期性和短暂的增加。假设环境GABA的周期性增加将激活突触后的GABAB受体并增强外突触性GABAA受体功能。在手术之前和过程中，将重复测量补品电流，以定期增加环境GABA。将使用三种方法来产生环境GABA的短暂增加。 1。周期性应用外源性GABA，2。刺激内源性GABA（电刺激，高K+）和3。诱导4-AP诱导无赞助者的临时放电。可以证实，使用GABAB受体拮抗剂CGP55845和含有G蛋白抑制剂（GDP-ß-S）的移液剂CGP55845和移液溶液，这些程序的作用是由突触后GABAB受体激活产生的。创伤性脑损伤（TBI）改变 海马中的GABAA受体功能。假设GPCR在实验性TBI后调节外突触性GABAA受体。我们将确定TBI对基本滋补电流的影响及其对GPCR的调节。具体而言，假设DGGC的滋补电流将通过TBI增强，部分原因是GPCR的激活增加。