Exploration of KCC2: Role in Schizophrenia

KCC2 的探索：在精神分裂症中的作用

• 批准号: 6677996
• 负责人: JOEL P GALLAGHER
• 金额: $ 15.1万
• 依托单位: UNIVERSITY OF TEXAS MED BR GALVESTON
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-15 至 2005-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6677996
• 关键词: GABA receptor; disease /disorder model; electrophysiology; furosemide; interneurons; ion transport; laboratory rat; membrane potentials; membrane transport proteins; neuropharmacology; neurophysiology; phencyclidine; potassium chloride; prefrontal lobe /cortex; protein structure function; pyramidal cells; schizophrenia; sectioning; synapses; tissue /cell preparation; transport inhibitor; voltage /patch clamp; western blottings

DESCRIPTION (provided by applicant): This is an exploratory/development grant (R21) proposal in response to NIMH RFA#PA-00-073. The K-CI Co-Transporter (KCC2) is neuronal specific and widely distributed in the central nervous system. KCC2 serves a dual function in neurons: the maintenance of low intracellular chloride ([CI]i) and the buffering of external potassium ([K]o) concentrations in the brain. Functionally, KCC2 is coupled with GABAA receptors whose activation allows anions (predominantly CI-) to flow into neurons, producing GABA's principal synaptic function - inhibition. Whether GABAA receptor activation leads to inhibition or excitation depends upon the value of its reversal potential (EGABAA). The reversal potential value is primarily determined by an electrochemical gradient of the CI across the membrane; KCC2 plays a pivotal role in regulating neuronal [Cl]i homeostasis. Thus, KCC2 regulates the physiological functions of GABAA receptors, namely, synaptic inhibition in normal adult CNS neurons, while also synaptic excitation in normal developing or neonatal neurons, and possibly - in a maladaptive manner - in disease affected neurons. The GABAergic system, the main inhibitory system in the brain, is reported to malfunction in schizophrenia (SCZ). SCZ is a complex mental disorder characterized by a debilitating disturbance of cognitive function and behavior that may result from a dysfunction of multiple CNS neurotransmission systems including the GABAergic system. However, the expression and function of the KCC2 transporter have not been studied in schizophrenic brains or in animal models of schizophrenia. We propose to explore the role of KCC2 in a chronic phencyclidine (c-PCP) rat model of schizophrenia. The experiments will test the hypothesis that in rats treated chronically with PCP, KCC2 is functionally down-regulated and/or its expression is altered in neurons of the medial prefrontal cortex (mPFC). The mPFC has long been implicated in the pathogenesis of schizophrenia. The specific aims are threefold: namely, 1) compare the synaptic physiology of GABAA receptors in the prefrontal cortex of normal and c-PCP rats; 2) determine the value of GABAA receptor reversal potentials (EGABAA), for GABAA receptors at synaptic and non-synaptic sites in normal and c-PCP rats, respectively; and, 3) determine the levels of protein expression of KCC2 while investigating its pharmacological manipulation with an antagonist, furosemide, in normal and c-PCP rats. Results from the proposed study may provide an impetus to consider a novel pathogenesis for schizophrenia, while at the same time providing a basis for a more effective pharmacotherapy.

描述（由申请人提供）：这是响应 NIMH RFA#PA-00-073 的探索/开发拨款 (R21) 提案。 K-CI 协同转运蛋白 (KCC2) 是神经元特异性的，广泛分布于中枢神经系统中。 KCC2 在神经元中具有双重功能：维持低细胞内氯 ([CI]i) 和缓冲大脑中的外部钾 ([K]o) 浓度。在功能上，KCC2 与 GABAA 受体结合，其激活使阴离子（主要是 CI-）流入神经元，产生 GABA 的主要突触功能 - 抑制。 GABAA 受体激活是否导致抑制或兴奋取决于其逆转电位（EGABAA）的值。反转电位值主要由跨膜 CI 的电化学梯度决定； KCC2 在调节神经元 [Cl]i 稳态中发挥着关键作用。因此，KCC2 调节 GABAA 受体的生理功能，即正常成人 CNS 神经元的突触抑制，同时也调节正常发育或新生儿神经元的突触兴奋，并且可能以适应不良的方式调节受疾病影响的神经元。据报道，GABA 能系统（大脑中的主要抑制系统）在精神分裂症 (SCZ) 中出现功能障碍。 SCZ 是一种复杂的精神障碍，其特征是认知功能和行为的衰弱性障碍，可能是由于包括 GABA 能系统在内的多个 CNS 神经传递系统功能障碍所致。然而，尚未在精神分裂症患者大脑或精神分裂症动物模型中研究 KCC2 转运蛋白的表达和功能。我们拟探讨 KCC2 在慢性苯环己哌啶 (c-PCP) 大鼠精神分裂症模型中的作用。这些实验将验证以下假设：在长期接受 PCP 治疗的大鼠中，内侧前额叶皮层 (mPFC) 神经元中的 KCC2 功能下调和/或其表达发生改变。 mPFC 长期以来一直被认为与精神分裂症的发病机制有关。具体目标有三个：即，1）比较正常大鼠和 c-PCP 大鼠前额皮质 GABAA 受体的突触生理学； 2)分别测定正常大鼠和c-PCP大鼠突触和非突触部位GABAA受体的GABAA受体反转电位(EGABAA)值； 3) 测定 KCC2 的蛋白表达水平，同时研究其在正常和 c-PCP 大鼠中使用拮抗剂呋塞米的药理学操作。拟议研究的结果可能会推动人们思考精神分裂症的新发病机制，同时为更有效的药物治疗提供基础。