GABA-A receptor plasticity: regulation by hypoxia

描述(申请人提供)：我们的长期目标是了解GABAA受体的可塑性如何参与维持中枢神经系统的功能。拟议的研究将检验两个GABAA受体亚基？6和？4的表达变化参与介导对缺氧的反应的假设。在以前对成年大鼠的研究中，我们发现持续的低压低氧选择性地触发从头开始的？6亚单位mRNA和蛋白的表达，并增加？4和？脑桥的亚单位信使核糖核酸水平，脑干区域参与维持内环境平衡。？6表达的诱导是值得注意的，因为这个亚基通常只在出生后的小脑中发现。更重要的是，在其他大脑区域，？6或？4与？在突触外的GABAA受体中，介导对基础水平的GABA的反应，即紧张性抑制。为了探讨GABAA受体可塑性在持续低氧反应中的作用，对野生型和？6或？4亚单位缺陷小鼠进行了分子、组织学和生理学研究，目的是：1)用qRT-PCR方法确定持续低压低氧对小鼠脑干GABAA受体亚单位mRNA表达的影响；2)定位表达？6和？4亚单位多肽的细胞，并用免疫组织化学和生化方法确定持续低氧后脑干中受体数量的变化；3)用全身体积描记法确定？4或？6 GABAA受体亚单位表达在持续低氧呼吸机反应中的重要性。这些研究的结果将开始确定用于适应低氧的分子机制，低氧应激在高海拔地区生理性地发生，并在包括慢性阻塞性肺疾病在内的几种病理条件下发生。具体地说，拟议的研究将提供对GABAA受体可塑性的贡献。我们的发现将为旨在了解参与维持大脑功能的回路的研究奠定基础。确定参与应对持续低氧的分子机制是创造新的治疗方法以对抗各种潜在威胁生命的疾病的关键的第一步。 与公共健康相关成熟的大脑适应环境压力的能力是生存所必需的。我们最近的发现提高了GABAA受体的可塑性，它介导了大脑中主要抑制性神经递质的活动，参与了介导对低氧的适应。缺氧是一种在许多生理和病理条件下发生的应激，包括高海拔生活和慢性阻塞性肺疾病。我们提出的研究的目的是证明GABAA受体亚单位的表达变化是适应低氧所必需的。确定与低氧反应有关的分子机制是创造新的治疗方法以对抗各种潜在威胁生命的情况的关键的第一步。

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.