GABA-A receptor plasticity: regulation by hypoxia

描述（由申请人提供）：我们的长期目标是了解GABAA受体的可塑性是如何参与维持中枢神经系统功能的，GABAA受体是一种五聚体配体门控离子通道。拟议的研究将检验两个GABAA受体亚基表达变化的假设，？6和？4、参与介导对还原氧的反应。在之前对成年大鼠的研究中，我们发现持续的低压缺氧选择性地触发新生？6亚基mRNA和蛋白表达增加？4和？脑桥的亚基mRNA水平，脑干区域参与维持体内平衡。的归纳？这种表达是值得注意的，因为这种亚基通常只存在于出生后的小脑中。更重要的是？6还是？4、在其他脑区，与？突触外GABAA受体介导对GABA基础水平的反应，即强直抑制。为了研究GABAA受体可塑性在野生型和野生型小鼠持续缺氧反应中的作用，对其进行了分子、组织学和生理学研究。6还是？4亚基缺陷小鼠：1)利用qRT-PCR检测持续低压缺氧对对照组或缺氧条件下小鼠脑干GABAA受体亚基mRNA表达的影响；2)定位表达？6和？4亚基多肽，并确定亚基水平的变化是否会改变脑干持续缺氧后的受体数量，使用免疫组织化学和生化方法；3)确定的重要性？4还是？6 GABAA受体亚基表达在持续缺氧通气反应中的全身体积脉搏图研究这些研究的结果将开始确定用于适应缺氧的分子机制，缺氧是在高海拔和包括慢性阻塞性肺病在内的几种病理条件下发生的生理应激。具体而言，所提出的研究将深入了解GABAA受体可塑性的贡献。我们的发现将为旨在了解维持大脑功能的回路的研究奠定基础。确定参与持续缺氧反应的分子机制是创造新的治疗方法来对抗各种潜在威胁生命的疾病的重要的第一步。

DESCRIPTION (provided by applicant): Our long term goal is to understand how plasticity of the GABAA receptor, a pentameric ligand-gated ion channel, participates in maintaining CNS function. The proposed studies will test the hypothesis that changes in expression of two GABAA receptor subunits, ?6 and ?4, participate in mediating the response to reduced oxygen. In previous studies on adult rats we found that sustained hypobaric hypoxia selectively triggers de novo ?6 subunit mRNA and protein expression and increases ?4 and ? subunit mRNA levels in the pons, a brainstem region involved in maintaining homeostasis. Induction of ?6 expression is notable because this subunit normally is found only in the postnatal cerebellum. More importantly, ?6 or ?4, in other brain regions, coassemble with ? in extrasynaptic GABAA receptors that mediate the response to basal levels of GABA, i.e., tonic inhibition. To investigate the role of GABAA receptor plasticity in the response to sustained hypoxia, molecular, histological, and physiologic studies on wild-type and ?6 or ?4 subunit-deficient mice are proposed to: 1) Determine how sustained hypobaric hypoxia alters GABAA receptor subunit mRNA expression in the brainstem of mice maintained in control or hypoxic conditions using qRT-PCR; 2) Locate cells that express the ?6 and ?4 subunit polypeptides and determine whether changes in subunit levels alter receptor number in the brainstem following sustained hypoxia using immunohistochemical and biochemical approaches; and 3) Determine the importance of ?4 or ?6 GABAA receptor subunit expression for the ventilatory response to sustained hypoxia using whole-body plethysmography. Findings from these studies will begin to define molecular mechanisms used in adapting to reduced oxygen, a stress that occurs physiologically at high altitude and in several pathological conditions, including chronic obstructive pulmonary diseases. Specifically, the proposed studies will provide insight into the contribution of GABAA receptor plasticity. Our findings will lay the groundwork for studies aimed at understanding the circuitry involved in maintaining brain function. Identifying the molecular machinery involved in the response to sustained hypoxia is an essential first step for creating novel therapeutic approaches to combat a variety of potentially life-threatening conditions. PUBLIC HEALTH RELEVANCE The ability of the mature brain to adapt to environmental stress is required for survival. Our recent findings raise the possibility that plasticity of the GABAA receptor, which mediates the actions of the major inhibitory neurotransmitter in the brain, participates in mediating adaptation to hypoxia. Oxygen deprivation is a stress that occurs during many physiological and pathological conditions, including life at high altitude and chronic obstructive pulmonary diseases. The goal of our proposed studies is to demonstrate that changes in the expression of specific GABAA receptor subunits are required for adaptation to hypoxia. Identifying the molecular machinery involved in the response to hypoxia is an essential first step for creating novel therapeutic approaches to combat a variety of potentially life-threatening situations.