Measuring and manipulating reward circuit plasticity in opiate addiction models

描述：阿片类药物成瘾是一个主要的健康问题，其慢性复发的性质可能是其最阴险的方面。在复吸之前，上瘾者在接触毒品或与毒品有关的刺激时经常会有强烈的渴望。面对成瘾的一个重要步骤是了解神经化学和细胞机制负责恢复药物使用后很久停止使用。伏隔核（NAc）是哺乳动物大脑中成瘾药物的关键靶点，并提供了药物观察行为背后的动力。虽然药物诱导的NAc ampa型谷氨酸受体（AMPARs）的可塑性在精神兴奋剂复发中得到了广泛的研究，但阿片诱导的可塑性的时间和解剖动力学以及这些适应性如何促进复发尚不清楚。在这里，我通过结合全细胞电生理学方法和病毒介导的光敏视蛋白表达（光遗传学），以及在药物给药的操作模型中荧光报告小鼠，研究了吗啡诱导的突触强度和皮质纹状体脑回路中谷氨酸相关可塑性的适应性。我们实验室的初步数据表明，在偶然和非偶然吗啡给药后（10-14天），NAc壳区MSN谷氨酸能突触强度增强。在K99 Aims中，我建议使用成瘾的扩展通路操作模型来描述含有多巴胺D1-(D1- msn)或D2-(D2- msn)受体亚型的NAc中棘神经元（msn）亚群中突触强度、谷氨酸受体信号传导和亚单位组成变化的时间过程和持续变化。接下来，我建议使用直接传递到NAc的光刺激选择性地激活表达通道视紫红质2到msn的皮层或杏仁核传入，以评估通路特异性可塑性的改变。K99阶段的训练将在

DESCRIPTION: Opiate addiction is a major health concern, and its chronic relapsing nature is perhaps its most insidious aspect. Preceding relapse, addicts often experience intense craving when exposed to drug or drug-associated stimuli. An essential step in confronting addiction is understanding the neurochemical and cellular mechanisms responsible for the resumption of drug use long after cessation of drug use. The nucleus accumbens (NAc) is a key target of addictive drugs in the mammalian brain and provides a motive force behind drug-seeing behavior. Although drug-induced plasticity in NAc AMPA-type glutamate receptors (AMPARs) has been studied extensively in psychostimulant relapse, the temporal and anatomical dynamics of opiate-induced plasticity and how these adaptations function to promote relapse is unknown. Here, I examine morphine- induced adaptations in synaptic strength and glutamate-related plasticity within corticostriatal brain circuits by combining whole-cell electrophysiologicl approaches with viral-mediated expression of light sensitive opsins (optogenetics), and fluorescent reporter mice in operant models of drug-administration. Pilot data from our lab indicate that MSN glutamatergic synaptic strength is potentiated in the NAc shell region following abstinence (10-14 days) from both contingent and non-contingent morphine administration. In the K99 Aims, I propose to delineate the time course of development and persistence of changes in synaptic strength, glutamate receptor signaling and subunit composition in subpopulations of NAc medium spiny neurons (MSNs) containing either the dopamine D1-(D1-MSN) or D2-(D2-MSN) receptor subtype using an extended-access operant model of addiction. Next, I propose to selectively activate channelrhodopsin2- expressing cortical or amygdalar afferents onto MSNs using optical stimulation delivered directly to the NAc to evaluate pathway-specific alterations in plasticity. Training in the K99 phase will be under the guidance of Dr. Mark Thomas, an expert in measuring glutamatergic synaptic function in reward circuits, whose lab has recently incorporated the use of optogenetics tools for in vitro and in viv study. We have recruited additional expertise from Drs. Tim Ebner (optogenetics/ mentorship), Antonello Bonci (optogenetics and behavior) and David Self (mouse drug self-administration) as part of my advisory committee. With the training in electrophysiology and optogenetic modulation of neural networks I receive during the K99 period, I will employ these techniques to further determine the functional role persistent opiate-induced plasticity plays in context-, cue-, and drug-induced relapse. Using in vivo optogenetic stimulation to depotentiate cortical and/or limbic afferents onto NAc MSNs, I predict that restoring "basal" neurotransmission prior to relapse testing using an established long-term depression protocol will prevent a subsequent return to opiate-seeking. Finally, I will use a novel model addiction model recently shown to promote compulsive-like drug-seeking in a subpopulation of mice to explore changes in excitatory and inhibitory neurotransmission neurons of the medial prefrontal cortex and dorsal striatum, two brain regions that have generally been overlooked in studies of opiate plasticity. These experiments will provide significant contributions to opiate addiction literature as well as potential pharmacotherapeutic targets to mitigate relapse.