Regulation of 5-HT circuits by CRF and GABA in opioid addiction and stress-induced relapse

压力影响阿片类药物成瘾的多个阶段，并与启动阿片类药物成瘾的更大脆弱性相关。 吸毒，更快地从药物使用过渡到滥用，以及更高的药物复发率，尽管神经系统 所涉及的电路和机制在很大程度上是未知的。越来越多的文献表明， 中缝背核（DRN）-5-羟色胺（5-HT）系统在一些情感性 促使吸毒和复吸的药物成瘾成分。急性阿片类刺激5-HT 通过GABA能去抑制的神经传递，可能有助于积极的情感成分， 阿片类药物成瘾早期寻求药物的动机。相比之下，在成瘾的后期，5-HT DRN系统可能 也有助于药物寻求通过其对压力源的反应和它的负面影响的动机。 与促肾上腺皮质激素释放因子（CRF）系统的相互作用。我们的实验室和其他实验室已经证明， CRF-R1受体通过GABA中间神经元抑制5-HT DRN神经元。初步数据显示， DRN-CRF回路中的神经适应与应激诱导的阿片类药物复发的脆弱性相关。 大鼠表达海洛因静脉自我给药（IVSA）或吗啡条件性给药消退 暴露在压力下的位置偏好（CPP）恢复了他们先前熄灭的海洛因寻求 行为或吗啡CPP，伴随着对5-HT DRN神经元的GABAA受体敏化的作用。 这种神经适应将使5-HT DRN神经元容易受到CRF-R1-GABA输入的抑制。从 根据这些数据，我们假设5-HT系统在阿片类药物成瘾中具有双重作用：1）早期阿片类药物成瘾 暴露刺激5-HT DRN神经元，产生积极的情感状态，有助于阿片奖励; 2） 有阿片类药物史的受试者的应激暴露使5-HT DRN神经元上的GABAA受体敏感， 它们容易受到位于GABA传入纤维上的CRF-R1的抑制。由此产生的5-羟色胺功能减退会导致 促使阿片类药物复吸的负面情感状态。在具体目标1中，我们将使用电生理学来 测量离体5-HT DRN神经元的膜特性和兴奋性的动态变化， 跟踪海洛因IVSA、消退和压力大鼠模型过程中的情感和行为变化- 诱导恢复。在具体的目标2中，我们将使用病毒递送设计者受体特异性激活 通过Designer Drugs在Tph 2-Cre大鼠中研究体内操纵5-HT DRN神经元活性的影响 在行为模型中。在具体目标3中，我们将在Crh-Cre或GAD-Cre大鼠中使用DREADD的病毒递送， 测试杏仁核CRF传入DRN和DRN GABA中间神经元之间的因果关系， 行为模型该建议采用多种离体和体内方法来剖析5-HT-1在细胞内的作用。 阿片类药物成瘾和复发模型中的GABA-CRF回路，最终目标是识别新的 治疗阿片类药物成瘾和预防复发的治疗目标。

Stress impacts multiple phases of opioid addiction and is associated with greater vulnerability to initiation of drug taking, more rapid transition from drug use to abuse, and higher rates of drug relapse, though the neural circuitry and mechanisms involved are largely unknown. A growing literature indicates the involvement of the dorsal raphe nucleus (DRN)-serotonin (5-hydroxytryptamine; 5-HT) system in some of the affective components of drug addiction that motivate drug taking and relapse. Acute opioids stimulate 5-HT neurotransmission via GABAergic disinhibition, potentially contributing a positive affective component to the motivation for drug seeking early in opioid addiction. By contrast, later in addiction, the 5-HT DRN system may also contribute to drug-seeking motivated by negative affect via its responsiveness to stressors and its interaction with the corticotropin-releasing factor (CRF) system. Our laboratory and others have shown that CRF-R1 receptors inhibit 5-HT DRN neurons via GABA interneurons. Preliminary data indicate a novel neuroadaptation within DRN-CRF circuits that is associated with vulnerability to stress-induced opioid relapse. Rats expressing extinction of either heroin intravenous self-administration (IVSA) or morphine conditioned place-preference (CPP) that are exposed to stress reinstate their previously extinguished heroin-seeking behavior or morphine CPP, an effect accompanied by sensitization of GABAA receptors on 5-HT DRN neurons. This neuroadaptation would render 5-HT DRN neurons vulnerable to inhibition by CRF-R1-GABA inputs. From these collective data, we hypothesize a dual role for the 5-HT system in opioid addiction: 1) early opioid exposure stimulates 5-HT DRN neurons, creating a positive affective state that contributes to opioid reward; 2) stress exposure in subjects with an opioid history sensitizes GABAA receptors on 5-HT DRN neurons, making them vulnerable to inhibition by CRF-R1 located on GABA afferents. The resulting 5-HT hypofunction creates a negative affective state that motivates opioid reinstatement. In specific aim 1, we will use electrophysiology to measure the dynamic changes in membrane properties and excitability of 5-HT DRN neurons ex vivo as they track with changes in affect and behavior over the course of a rat model of heroin IVSA, extinction and stress- induced reinstatement. In specific aim 2 we will use viral delivery of Designer Receptor Exclusively Activated by Designer Drugs in Tph2-Cre rats to examine the impact of manipulating 5-HT DRN neuronal activity in vivo in the behavioral model. In specific aim 3 we will use viral delivery of DREADDs in Crh-Cre or GAD-Cre rats to test the causal relationship between amygdala CRF afferents to the DRN and DRN GABA interneurons in the behavioral model. This proposal employs multiple ex vivo and in vivo approaches to dissect the role of 5-HT- GABA-CRF circuitry in a model of opioid addiction and relapse with the ultimate goal of identifying novel therapeutic targets to treat opioid addiction and prevent relapse.