CHOLINERGIC REGULATION IN THE HYPOTHALAMUS

描述（由申请人提供）：谷氨酸是中枢神经系统（CNS）大部分区域（包括下丘脑）主要的快速兴奋性神经递质。在使用抗谷氨酸受体药物（包括一些滥用药物）、谷氨酸能神经元或突起的选择性变性和胚胎发育期间，可以发现谷氨酸活性水平下降。其他实验室的观察结果显示，在这三种情况下，中枢神经系统的胆碱能功能都有所增加。我们最近在下丘脑神经元培养中进行的实验表明，慢性阻断嗜离子性谷氨酸受体可显著增加兴奋性乙酰胆碱（ACh）突触活性和胆碱能神经元的数量。资料提示，在体外下丘脑谷氨酸传递长期减少的过程中，通常在下丘脑中仅表现出弱活性的乙酰胆碱发挥了主要兴奋性神经递质的作用，并支持兴奋/抑制平衡。我们还假设，兴奋性乙酰胆碱传递的增加代表了一种新的神经元可塑性形式，在谷氨酸兴奋减少时调节神经元的活动和兴奋性。然而，谷氨酸依赖性调节中枢神经系统乙酰胆碱传递的机制尚未被研究。它们将在下丘脑神经元的拟议研究中进行研究。首先，利用大鼠下丘脑培养，我们将验证在谷氨酸传递减少过程中乙酰胆碱和谷氨酸从相同的突触末端共同释放的假设。其次，使用下丘脑培养，我们将验证神经元中胆碱能表型的诱导是通过creb依赖的信号转导途径调节的假设。第三，我们将验证长期阻断大鼠体内谷氨酸NMDA受体会增加下丘脑神经元胆碱能表型特性的预测。这将通过电生理学、钙离子成像、免疫染色和分子生物学进行研究。本项目旨在研究谷氨酸兴奋降低时神经元回路中神经元可塑性和神经元活动调控的基本机制。鉴于谷氨酸受体拮抗剂用于患者的慢性治疗，并且一些谷氨酸受体拮抗剂是滥用药物，本研究获得的数据可能具有重要的临床相关性。

DESCRIPTION (provided by applicant): Glutamate is the major fast excitatory neurotransmitter in most regions of the central nervous system (CNS), including the hypothalamus. A decreased level of glutamate activity can be found during the use of antiglutamate receptor drugs (including some drugs of abuse), selective degeneration of glutamatergic neurons or projections, and embryonic development. Observations from other laboratories revealed increased cholinergic functions in the CNS during each of these three conditions. Our recent experiments in hypothalamic neuronal cultures indicated that a chronic blockade of ionotropic glutamate receptors dramatically increases excitatory acetylcholine (ACh) synaptic activity and the number of cholinergic neurons. Data suggested that during a long-term decrease in glutamate transmission in the hypothalamus in vitro, ACh, which normally exhibits only weak activity in the hypothalamus, plays the role of the major excitatory neurotransmitter and supports the excitation/inhibition balance. We also hypothesized that an increase in excitatory ACh transmission represents a novel form of neuronal plasticity that regulates the activity and excitability in neurons during a decrease in glutamate excitation. However, the mechanisms of glutamate-dependent regulation of ACh transmission in the CNS have not been studied. They will be studied in the proposed research in hypothalamic neurons. First, using rat hypothalamic cultures, we will test the hypothesis that during decrease in glutamate transmission ACh and glutamate are co-released from the same synaptic terminals. Second, using hypothalamic cultures, we will test the hypothesis that the induction of cholinergic phenotype in neurons is regulated through a CREB-dependent signal transduction pathway. Third, we will test the prediction that a chronic blockade of glutamate NMDA receptors in rats in vivo increases cholinergic phenotypic properties in hypothalamic neurons. This will be studied using electrophysiology, Ca 2+ imaging, immunostaining, and molecular biology. This project addresses the fundamental mechanisms of neuronal plasticity and regulation of neuronal activity that can take place in neuronal circuits during a decrease in glutamate excitation. Data obtained here may have an important clinical relevance, given that glutamate receptor antagonists are used for chronic treatment of patients, and some glutamate receptor antagonists are drugs of abuse.