Neuronal regulation of glutamate homeostasis

谷氨酸稳态的神经调节

• 批准号: 8893512
• 负责人: PAUL ALLEN ROSENBERG
• 金额: $ 27.9万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-17 至 2017-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8893512
• 关键词: Acute; Affect; Amphetamines; Animals; Anxiety; Astrocytes; Behavior; Behavioral; Biochemical; Brain; Brain region; Cell physiology; Chronic; Cognitive; Defect; Disease; Dopamine; Dopamine D1 Receptor; Dopamine D2 Receptor; Excitatory Synapse; Exposure to; Functional disorder; Gene Expression; Glutamate Transporter; Glutamates; Hippocampus (Brain); Homeostasis; Immediate-Early Genes; Knock-out; Knockout Mice; Light; Locomotion; Measures; Mediating; Membrane Potentials; Mental disorders; Modeling; Molecular; Mus; N-Methyl-D-Aspartate Receptors; N-Methylaspartate; NMDA receptor antagonist; Neurobehavioral Manifestations; Neurons; Parvalbumins; Pathogenesis; Patients; Performance; Phenotype; Preparation; Presynaptic Terminals; Publishing; Regulation; Rest; Role; Schizophrenia; Short-Term Memory; Signal Transduction; Slice; Subchronic Schizophrenia; Symptoms; Synapsins; Synaptic Transmission; Testing; Thalamic structure; Wolves; Work; dopamine transporter; dopaminergic neuron; drug discovery; extracellular; glutamatergic signaling; improved; mind control; novel; nucleus reticularis; object recognition; promoter; public health relevance; recombinase; relating to nervous system; resilience; response; stem; therapeutic target

 DESCRIPTION (provided by applicant): Schizophrenia is a chronic, devastating, psychiatric disorder characterized attributed to abnormalities in dopamine and glutamate signaling. Excitatory circuits control the activity of dopamine neurons, and it is thought that abnormalities in these circuits produce the positive, negative and cognitive features of schizophrenia. Glutamate homeostasis refers to the control of glutamate levels in and around excitatory synapses, and we now have evidence that glutamate homeostasis might be important in controlling the circuits involved in schizophrenia. Glutamate transporters control brain glutamate homeostasis, and the major glutamate transporter in the brain is GLT-1, primarily expressed in astrocytes. Others and we have found that GLT-1 is also expressed in excitatory presynaptic terminals. To understand the function of GLT-1 expressed in neurons, we generated a conditional GLT-1 knockout mouse in which we have used synapsin-cre to accomplish the selective inactivation of GLT-1 in neurons. We have performed extensive behavioral phenotyping of this mouse, including testing responses to amphetamine, which are highly modulated by excitatory signaling and therefore likely, we thought, to be affected by glutamate dyshomeostasis. Previous work by many groups has demonstrated the phenomenon of sensitization to amphetamine, in which behavioral or neural (i.e. dopamine release) effects increase with repeated administration. Amphetamine sensitization is thought to model the cellular processes that underlie the positive symptoms of schizophrenia. Remarkably, we found that inactivation of GLT-1 in neurons produced significant decrease in the acute and sensitized locomotor responses to amphetamine. In addition, we have found improved performance of the nGLT-1 KO in novel object recognition and light-dark emergence. Defects on NOR and LDE may reflect impaired working memory and increased anxiety, components of the cognitive and negative domain of symptoms of schizophrenia. These observations have led us to hypothesize that the nGLT-1 KO may demonstrate resilience to the biochemical and circuit disturbances associated with schizophrenia. We hypothesize further that the phenotype that we observe in the nGLT-1 KO partially stems from changes in ambient glutamate within regions of the brain dependent upon neuronal GLT-1 for glutamate homeostasis. We propose to characterize these phenotypes further to establish whether GLT-1 may be valid target for therapeutic drug discovery. Toward that end, we will: 1) characterize the behavioral phenotype of the nGLT-1 KO mouse subjected to subchronic PCP administration to model symptom domains observed in schizophrenia; 2) characterize the biochemical phenotype of nGLT-1 KO mice; 3) determine the effect of neuronal knockout of GLT-1 on glutamate homeostasis in the nucleus reticularis slice preparation.

 描述（由申请人提供）：精神分裂症是一种慢性、破坏性的精神疾病，其特征在于多巴胺和谷氨酸信号传导异常。兴奋回路控制多巴胺神经元的活动，人们认为这些回路的异常会产生精神分裂症的积极、消极和认知特征。谷氨酸稳态是指兴奋性突触内和周围谷氨酸水平的控制，我们现在有证据表明，谷氨酸稳态可能在控制精神分裂症相关回路方面很重要。谷氨酸转运蛋白控制大脑谷氨酸稳态，大脑中主要的谷氨酸转运蛋白是GLT-1，主要在星形胶质细胞中表达。我们还发现GLT-1在兴奋性突触前末梢也有表达。为了了解神经元中表达的GLT-1的功能，我们产生了条件性GLT-1敲除小鼠，其中我们使用突触蛋白cre来实现神经元中GLT-1的选择性失活。我们已经对这只小鼠进行了广泛的行为表型分析，包括测试对安非他明的反应，安非他明受到兴奋性信号的高度调节，因此我们认为可能受到谷氨酸稳态障碍的影响。许多小组先前的工作已经证明了安非他明的致敏现象，其中行为或神经（即多巴胺释放）效应随着重复给药而增加。安非他明致敏被认为是精神分裂症阳性症状背后的细胞过程的模型。值得注意的是，我们发现神经元中GLT-1的失活导致对苯丙胺的急性和致敏运动反应显著降低。此外，我们已经发现nGLT-1 KO在新物体识别和明暗出现方面的性能有所改善。NOR和LDE的缺陷可能反映了工作记忆受损和焦虑增加，这是精神分裂症症状的认知和消极领域的组成部分。这些观察结果使我们假设nGLT-1 KO可能表现出对与精神分裂症相关的生化和电路紊乱的弹性。我们进一步假设，我们在nGLT-1 KO中观察到的表型部分源于依赖于神经元GLT-1的谷氨酸稳态的大脑区域内环境谷氨酸的变化。我们建议进一步表征这些表型，以确定GLT-1是否可能是治疗药物发现的有效靶点。为此，我们将：1）表征经受亚慢性PCP施用的nGLT-1 KO小鼠的行为表型以模拟精神分裂症中观察到的症状域; 2）表征nGLT-1 KO小鼠的生化表型; 3）确定GLT-1的神经元敲除对网状核切片制备物中谷氨酸稳态的影响。