CaV 1.3 L-type Calcium Channel Mechanisms in Cocaine Seeking

描述（由申请人提供）：成功治疗可卡因成瘾的一个主要障碍是在戒毒期间发生的高药物复发率。暴露于与毒品有关的线索，诱发可卡因渴求和可卡因寻求行为，可加速可卡因复发。然而，到目前为止，还没有FDA批准的药物疗法来治疗可卡因成瘾。因此，我们了解可卡因寻求行为的神经生物学机制是至关重要的，这样才能确定新的治疗靶点，以防止这种复发性疾病。药物相关的线索引起腹侧被盖区（VTA）多巴胺（DA）神经元的突然放电，导致伏隔核（NAc）的阶段性DA释放。我们实验室的研究表明，VTA到NAc回路的相性DA活性，以及VTA胆碱能受体对这种活性的调节，对线索诱导的可卡因寻求至关重要。然而，在可卡因戒断期间，介导阶段性多巴胺释放和线索诱导的觅药行为的确切机制仍然知之甚少。我们之前已经表明，在长时间戒断后，VTA DA神经元中的Cav1.3 l型Ca2+通道（ltcc）及其下游Ca2+激活通路对于可卡因致敏的精神运动行为反应至关重要。此外，我们最近的研究结果表明，Cav1.3通道促进DA神经元从强直放电到突发放电的转变，并通过胆碱能机制起作用，这强烈表明Cav1.3通道的募集可能是线索诱导的可卡因寻求行为的基础。因此，本R21应用的目的是验证VTA Cav1.3机制通过调节NAc的阶段性DA释放来支持线索诱导的可卡因寻求行为的假设。为了实现这一目标，我们将采用一种创新的综合实验方法，利用药理学和病毒载体介导的VTA基因敲低，结合行为测试和NAc体内伏安法，在临床前自我给药大鼠模型中检测戒断期间线索诱导的可卡因寻求。在具体目标1中，我们将研究VTA Cav1.3通道在早期和长期戒断期间线索诱导的可卡因寻求中的作用。在具体目标2中，我们将在体内研究VTA Cav1.3通道在早期和长期戒断期间VTA诱发的和乙酰胆碱受体介导的NAc相DA释放中的作用。从这项研究中获得的机制见解将为药物复发的神经生物学提供新的理解，并将确定Cav1.3通道是否可能作为预防可卡因复发的潜在新治疗靶点。

DESCRIPTION (provided by applicant): A major barrier to successfully treating cocaine addiction is the high rate of drug relapse that occurs during periods of drug withdrawal. Cocaine relapse can be precipitated by exposure to drug-associated cues that induce cocaine craving and cocaine-seeking behavior. However, to date there are no FDA approved pharmacotherapies to treat cocaine addiction. Thus it is crucial that we understand the neurobiological mechanisms of cocaine-seeking behavior to be able to identify novel therapeutic targets to prevent this relapsing disorder. Drug-associated cues evoke burst firing of ventral tegmental area (VTA) dopamine (DA) neurons that results in phasic DA release in the nucleus accumbens (NAc). Work from our laboratory has revealed that phasic DA activity in the VTA to NAc circuit, and VTA cholinergic receptor regulation of such activity, is critical for cue-induced cocaine-seeking. However, the precise mechanisms that mediate phasic dopamine release and cue-induced drug-seeking behavior during cocaine withdrawal remain poorly understood. We have previously shown that Cav1.3 L-type Ca2+ channels (LTCCs) and their downstream Ca2+-activated pathways in VTA DA neurons are critical for sensitized psychomotor behavioral responses to cocaine following periods of prolonged withdrawal. Additionally our recent findings have revealed that Cav1.3 channels facilitate the transition of DA neurons from tonic to burst firing and act through cholinergic mechanisms, strongly suggesting that recruitment of Cav1.3 channels may underlie cue-induced cocaine-seeking behavior. Thus, the goal of this R21 application is to test the hypothesis that VTA Cav1.3 mechanisms underlie cue-induced cocaine-seeking behavior by regulating phasic DA release in the NAc. To achieve this goal, we will use an innovative and integrative experimental approach using pharmacology and viral vector-mediated genetic knockdown in the VTA in combination with behavioral testing and in vivo voltammetry in the NAc, to examine cue-induced cocaine seeking during withdrawal, using the preclinical self-administration rat model. In specific aim 1, we will examine the role of VTA Cav1.3 channels in cue-induced cocaine-seeking during early and protracted withdrawal. In specific aim 2, we will examine in vivo the role of VTA Cav1.3 channels in VTA-evoked- and acetylcholine receptor-mediated phasic DA release in the NAc during early and protracted withdrawal. The mechanistic insight gained from this study will provide new understanding of the neurobiology of drug relapse and will determine whether Cav1.3 channels may serve as a potential novel therapeutic target to prevent cocaine relapse.