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

应激影响阿片成瘾的多个阶段，并与更容易引发阿片成瘾有关 吸毒，从吸毒到滥用的更快转变，以及更高的药物复发率，尽管神经 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-羟色胺；5-羟色胺)系统在部分情感性神经元中的表达 导致吸毒和复发的吸毒成瘾的组成部分。急性阿片类药物刺激5-羟色胺 通过GABA能去抑制的神经传递，潜在地对 阿片成瘾早期寻求药物的动机。相比之下，在后来的成瘾中，5-HTDRN系统可能 也有助于通过对应激源的反应性和 与促肾上腺皮质激素释放因子(CRF)系统相互作用。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-HTDRN神经元。初步数据显示一部小说 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有关。 海洛因静脉给药(IVSA)或吗啡条件性戒断的大鼠 暴露在压力下的位置偏爱(CPP)恢复了他们之前停止的海洛因寻找 行为或吗啡CPP，伴随着GABAA受体对5-HTDRN神经元的敏化作用。 这种神经适应将使5-羟色胺DRN神经元容易受到CRF-R1-GABA输入的抑制。从… 这些集体数据，我们假设5-羟色胺系统在阿片成瘾中起双重作用：1)早期阿片成瘾 暴露刺激5-羟色胺DRN神经元，创造一种积极的情感状态，有助于阿片类药物的奖励；2) 有阿片病史的受试者应激暴露使5-羟色胺DRN神经元上的GABAA受体敏感，使 它们易受位于GABA传入纤维上的CRF-R1的抑制。由此产生的5-羟色胺功能减退导致 激发阿片类药物恢复的负面情绪状态。在具体目标1中，我们将使用电生理学来 测定体外培养的5-羟色胺背根神经元膜特性和兴奋性的动态变化 跟踪海洛因静脉注射、戒断和应激大鼠模型中情感和行为的变化- 诱导复职。在特定目标2中，我们将使用病毒传递独家激活的Designer受体 通过设计药物在TPH2-CRE大鼠体内检测操纵5-羟色胺DRN神经元活动的影响 在行为模型中。在特定目标3中，我们将在CRH-CRE或GAD-CRE大鼠中使用DREADDS的病毒传递来 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。本研究采用多种体外和体内实验方法来研究5-羟色胺的作用。 阿片成瘾和复发模型中的GABA-CRF回路，最终目的是识别新的 治疗目标是治疗阿片成瘾和防止复发。

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.