Mu receptors and ethanol/dopamine interactions

描述(申请人提供)：有助于控制酒精饮酒行为的神经化学和细胞机制尚不完全清楚，但多巴胺参与中脑边缘系统的假设已经有一段时间了。已知许多神经化学系统调节中脑边缘多巴胺系统的活性，例如阿片肽及其受体。纳曲酮是一种广谱阿片受体拮抗剂，是临床上用于减少酒精中毒复发的有效药物，但其具体作用机制尚不清楚。MU阿片受体在解剖学上位于腹侧被盖区(VTA)，已知通过抑制GABA中间神经元来控制VTA多巴胺神经元的活动。然而，这一机制在乙醇调节多巴胺释放中的作用，以及特定阿片受体亚型的作用还没有确定。我们的初步研究表明，Mu阿片受体参与了乙醇刺激腹侧纹状体多巴胺释放的机制，腹侧纹状体是中脑边缘系统的终末区域之一。我们建议确定阿片受体的基因缺失或不可逆阻断是否会改变酒精刺激的腹侧纹状体多巴胺释放的剂量-反应曲线(目标1)。我们建议使用的遗传模型将是建立在C57BL/6背景上的同源mU受体敲除和野生型对照。这些研究还将通过使用纳洛酮对Mu受体不可逆阻断的效果进行研究来补充。我们还将使用两瓶选择程序(目标2)来确定Mu受体的缺失或不可逆转的封锁是否会改变乙醇的消耗。此外，我们建议确定腹侧被盖区或腹侧纹状体的Mu受体是否参与了Mu受体功能丧失对乙醇刺激的多巴胺释放的抑制作用(目标3)。这将通过向任一区域微量注射纳洛酮并测量乙醇反应来完成。通过对GABA能中间神经元细胞和突触活动的电生理测量(目标4)，将检验Mu受体在VTA-多巴胺神经元控制中的作用。这些研究将利用如上所述的遗传学和药理学方法。总之，拟议的实验将阐明Mu阿片受体在乙醇调节中脑边缘多巴胺活性中的作用。

DESCRIPTION (provided by applicant): The neurochemical and cellular mechanisms that contribute to the control of ethanol drinking behavior are not fully understood, but the involvement of dopamine in the mesolimbic system has been hypothesized for some time. Many neurochemical systems are known to regulate the activity of the mesolimbic dopamine system, e.g., the opiate peptides and their receptors. Naltrexone, a clinically effective drug used to reduce relapse in alcoholism, is a broad spectrum opiate receptor antagonist, but its mechanism is not known in detail. Mu opiate receptors are anatomically located in the ventral tegmental area (VTA) and are known to control VTA dopamine neuron activity through the inhibition of GABA interneurons. However, the role of this mechanism in ethanol's regulation of dopamine release, and the role of particular opiate receptor subtypes has not been firmly established. Our preliminary studies show that mu opiate receptors are involved in the mechanism by which ethanol stimulates dopamine release in the ventral striatum, one of the terminal areas of the mesolimbic system. We propose to determine whether genetic deletion or irreversible blockade of the mu opiate receptor alters the dose-response curve for ethanol-stimulated dopamine release in the ventral striatum (aim 1). The genetic model we propose to use will be congenic mu receptor knockouts and wild-type controls that have been established on a C57BL/6 background. These studies will be complemented by investigation of effects of irreversible blockade of mu receptors with the use of naloxonazine. We also will determine whether the deletion of the mu receptor or irreversible blockade alters ethanol consumption using a two bottle choice procedure (aim 2). Moreover, we propose to determine whether mu receptors in the ventral tegmental area or the ventral striatum are involved in the inhibitory effects of loss of mu receptor function on ethanol stimulated dopamine release (aim 3). This will be done by microinjection of naloxonazine into either area and measuring the ethanol response. The role of mu receptors in the control of VTA-dopamine neurons will be examined using electrophysiological measures of cellular and synaptic activity in GABAergic interneurons (aim 4). These studies will utilize both the genetic and pharmacological approaches as described above. Together, the proposed experiments will elucidate the role of mu opiate receptors in the modulation of mesolimbic dopamine activity by ethanol.