GABAergic Sensitization of the Serotonin System in Stress-Induced Opiate Relapse

描述（由申请人提供）：阿片类药物是有效的镇痛剂，但也有很高的滥用倾向。即使在长期禁欲之后，前阿片类药物成瘾者仍然容易复发，特别是在压力条件下。阿片类药物成瘾和复发机制的大部分焦点集中在传统的多巴胺能奖励途径。很少有研究探讨5-羟色胺（5-HT）系统在阿片类药物成瘾和复发中的作用。啮齿类动物的初步数据表明，应激与阿片类药物史相互作用，使5-HT中缝背核（DRN）神经元对GABA能抑制敏感。最近的工作确定了DRN中的GABA信号传导与应激诱导的阿片类物质恢复之间的因果关系。我们假设，这种GABA能敏感化会导致血清素能功能低下和随之而来的烦躁情绪状态，从而驱动寻求药物的行为，从而容易受到压力诱导的阿片类药物复发的影响。在本申请中，我们将采用两种最先进的遗传突变策略，使用Cre-loxP系统来工程化选择性地在DRN或特别是在5-HT神经元中缺乏GABAA受体的小鼠。首先，我们将确认DRN或5-HT特异性缺失的GABAA受体在这些小鼠中使用免疫组织化学，电生理学和定量放射自显影。接下来，我们将在两个互补的复发动物模型中测试这些小鼠，其中游泳应激用于恢复先前熄灭的吗啡条件性位置偏好或自我给药。我们预测，这些小鼠将受到保护，从GABA能敏化观察到的5-HT DRN系统后，应激诱导的复发模型，因此将不太容易复发，在这两个模型。这些研究将产生创新的阿片类药物复吸抗性的动物模型，这将是一个有价值的工具，以阐明新的电路内的5-HT DRN系统，有助于阿片类药物复吸。这种方法可以确定新的目标，阿片类药物成瘾的治疗和预防复发。

DESCRIPTION (provided by applicant): Opioids are effective analgesics but also carry a high abuse liability. Even after prolonged abstinence, former opioid addicts can remain vulnerable to relapse, particularly under stressful conditions. Most of the focus on opioid addiction and relapse mechanisms have centered on traditional dopaminergic reward pathways. Fewer studies have examined the role of the serotonin (5-hydroxytryptamine; 5-HT) system in opioid addiction and relapse. Preliminary data in rodents indicate that stress interacts with opioid history to sensitize 5-HT dorsal raphe nucleus (DRN) neurons to GABAergic inhibition. More recent work identified a causal relationship between GABA signaling in the DRN and stress-induced opioid reinstatement. We hypothesize that this GABAergic sensitization results in serotonergic hypofunction and consequent dysphoric mood states which drive drug-seeking behaviors and therefore confer vulnerability to stress- induced opioid relapse. In the current application, we will employ two state-of-the-art genetic mutational strategies using the Cre-loxP system to engineer mice that are deficient in GABAA receptors selectively in the DRN or specifically in 5-HT neurons. First, we will confirm DRN- or 5-HT-specific deletion of the GABAA receptor in these mice using immunohistochemistry, electrophysiology and quantitative autoradiography. Next, we will test these mice in two complementary animal models of relapse in which a swim stress is used to reinstate previously extinguished morphine conditioned place-preference or self-administration. We predict that these mice will be protected from the GABAergic sensitization observed in the 5-HT DRN system following a stress-induced relapse model and will thus be less vulnerable to relapse in these two models. These studies will generate innovative animal models of opiate relapse resistance that will be a valuable tool to elucidate novel circuitry within the 5-HT DRN system that contribute to opiate relapse. This approach may identify novel targets for the treatment of opiate addiction and the prevention of relapse.