Regulation of VTA dopamine neurons by AMP kinase

描述(由申请人提供)：腹侧被盖区(VTA)神经元释放的多巴胺有助于学习目标导向的行为，并调节大多数滥用药物的愉悦方面。如果要了解多巴胺释放是如何控制的，就必须了解VTA神经元的兴奋性是如何受到突触输入和膜特性的调节的。5‘-单磷酸腺苷(AMP)激活的蛋白激酶(AMPK)是调节细胞代谢的主酶。在外周组织中，AMPK激活生化途径，增加能量生产，同时减少能量消耗。虽然它在大脑中广泛表达，但在中枢神经元中的功能在很大程度上是未知的。我们实验室的初步数据表明，AMPK激动剂增强了ATP敏感K+(K-ATP)通道诱发的超极化电流，减少了多巴胺D2自身受体的脱敏，并抑制了VTA神经元兴奋性突触传递的影响。我们提出的研究的总体假设是，AMPK的激活增强了对VTA神经元的抑制影响。斑片吸管将被用来记录大鼠中脑切片中单个VTA神经元的全细胞电流和电位。Western免疫印迹将用于量化在存在和不存在AMPK激活剂和/或抑制剂的情况下孵育的中脑片中磷酸化和非磷酸化AMPK的水平。目的#1研究AMPK激动剂对K-ATP开放剂二氮嗪诱发电流的影响。目的#2将研究第二信使系统，并确定介导AMPK激活剂减少多巴胺D2自身受体脱敏能力的递质受体。目的#3将研究AMPK抑制VTA内谷氨酸介导的突触传递的机制和作用部位。目的#4将描述AMPK激活抑制VTA多巴胺神经元爆发放电的机制。这些研究的结果可能会为治疗多巴胺依赖性疾病提供新的药理策略。

DESCRIPTION (provided by applicant): Dopamine release from ventral tegmental area (VTA) neurons assists in learning goal-oriented behaviors and mediates the pleasurable aspects of most drugs of abuse. Understanding how the excitability of VTA neurons is regulated by synaptic inputs and membrane properties is crucial if one is to understand how dopamine release is controlled. 5'-Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a master enzyme that regulates cellular metabolism. In peripheral tissues, AMPK activates biochemical pathways that increase energy production while reducing energy expenditure. Although widely expressed in brain, its function in central neurons is largely unknown. Preliminary data from our lab suggest that activators of AMPK potentiate the hyperpolarizing current evoked by ATP-sensitive K+ (K-ATP) channels, reduce the desensitization of dopamine D2 autoreceptors, and inhibit the influence of excitatory synaptic transmission in VTA neurons. The over-arching hypothesis of our proposed studies is that AMPK activation augments inhibitory influences on VTA neurons. Patch pipettes will be used to record whole-cell currents and potentials in single VTA neurons in slices of rat midbrain. Western immunoblot will be used to quantify levels of phosphorylated and unphosphorylated AMPK in midbrain slices that have been incubated in the presence and absence of AMPK activators and/or inhibitors. Aim #1 will characterize the effect of AMPK activators on currents evoked by the K- ATP opener diazoxide. Aim #2 will investigate second messenger systems and identify transmitter receptors that mediate the ability of AMPK activators to reduce dopamine D2 autoreceptor desensitization. Aim #3 will investigate mechanisms and sites of action by which AMPK inhibits glutamate-mediated synaptic transmission in the VTA. Aim #4 will characterize mechanisms by which AMPK activation inhibits burst firing in VTA dopamine neurons. Results of these studies may suggest new pharmacological strategies for treating dopamine-dependent disorders.