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行为，并介导大多数滥用药物的愉快方面。了解腹侧被盖区神经元的兴奋性如何受突触输入和膜特性的调节是至关重要的，如果要了解多巴胺的释放是如何控制的。5 '-腺苷一磷酸（AMP）激活的蛋白激酶（AMPK）是调节细胞代谢的主要酶。当被AMP/ATP比率下降激活时，AMPK促进生物化学途径，增加能量产生，同时减少能量消耗。虽然AMPK被广泛认为是一种能量传感器，但最近的研究表明它也影响神经元的兴奋性。我们实验室的初步数据表明，AMPK激活剂增强ATP敏感性K+（K-ATP）通道诱发的超极化电流，减少多巴胺D2自受体的脱敏，并抑制VTA神经元兴奋性突触传递的影响。我们提出的研究过度假设是AMPK激活增强了对VTA神经元的抑制作用。将使用膜片移液管记录大鼠中脑切片中单个VTA神经元的全细胞电流和电位。蛋白质免疫印迹将用于定量在存在和不存在AMPK激活剂和/或抑制剂的情况下孵育的中脑切片中磷酸化和总AMPK的水平。目的#1将表征AMPK激活剂对由K-ATP开放剂二氮嗪诱发的电流的影响。目标#2将研究第二信使系统，并确定介导AMPK激活剂降低多巴胺D2自身受体脱敏能力的递质受体。目的#3将研究AMPK抑制腹侧被盖区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激活抑制腹侧被盖区多巴胺神经元爆发放电的机制。这些研究的结果可能为治疗多巴胺依赖性疾病提出新的药理学策略。

DESCRIPTION (provided by applicant): Dopamine release from neurons in the ventral tegmental area (VTA) 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. When activated by a falling AMP/ATP ratio, AMPK promotes biochemical pathways that increase energy production while reducing energy expenditure. Although AMPK is widely regarded as an energy sensor, recent studies suggest it also influences neuronal excitability. 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 total 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.