PACAP-Dependent Coordination of Glutamate Signaling between Neurons and Astrocytes

项目概要/摘要 谷氨酸信号传导失调是药物成瘾病理基础的核心组成部分，涉及 可卡因和许多其他物质。神经科学和其他领域的最新进展清楚地表明 谷氨酸编码信号的分子和细胞基础比以前复杂得多 认可。特别是，越来越明显的是，星形胶质细胞是最重要的细胞之一。 人脑中丰富的细胞释放谷氨酸，对神经回路活动产生复杂的调节。 这种谷氨酸编码的细胞间信号传导的新形式可能对于理解病理学至关重要 长期使用药物产生的谷氨酸由于星形胶质细胞的谷氨酸释放机制，如系统 xc- (Sxc) 被可卡因改变。虽然这些发现提出了许多可能至关重要的问题 为了了解人脑中的谷氨酸信号传导，该提案将重点关注以下问题：如何 神经元调节星形胶质细胞的谷氨酸释放，以控制与相关的神经网络活动和行为 可卡因成瘾。我们将检验这一假设，即这是通过神经肽垂体的作用实现的 腺苷酸环化酶激活多肽（PACAP），我们认为它是腺苷酸环化酶激活多肽的一个未被识别的成分 伏隔核 (NAc) 中的谷氨酸信号传导。作为支持，我们发现 A) PACAP mRNA 是 在 NAc 传入细胞中表达，B) PACAP 受体在 NAc 星形胶质细胞和投射到的神经元中表达 PACAP 刺激黑质 (SN) 但不是腹侧苍白球 (VP)，C) PACAP 刺激谷氨酸释放 星形胶质细胞通过增加系统 xc- (Sxc) 的活性，D) PACAP 应用抑制 NAc 中的 eEPSC 中型多棘神经元 (MSN) 投射到黑质 (SN)，但不投射到腹侧苍白球，E) PACAP 的 NAc 内微量输注可阻止可卡因恢复。在这个提案中，我们将测试假设 PACAP 是一种神经肽，可调节星形胶质细胞和谷氨酸受体的谷氨酸释放 神经元提供一种新形式的 NAc 传出通路的通路特异性调节。在目标 1 中，我们将 检查 PACAP 诱导的 Sxc 活性增加的分子基础，并确定 Sxc 是否 PACAP 必须进行监管才能抑制 NAc-SN MSN 中的 eEPSC 并阻止可卡因恢复。在 为了这个目标，我们还将检查 PACAP 是否会增加星形胶质细胞释放机制中的谷氨酸 SXC。在目标 2 中，我们将研究 PACAP 触发的星形胶质细胞-神经元信号传导形式的可能性 需要神经元谷氨酸受体的调节以产生相关的生理变化，从而控制 NAc 传出神经和行为的输出。我们还将探讨 PACAP 是否会改变突触前谷氨酸 释放。在目标 3 中，我们将研究内源性 PACAP 的作用，以了解这种神经肽是否是一种 NAc 中谷氨酸信号传导中未被识别的成分，以及它是否是药物的关键决定因素 寻求行为。

Project Summary/Abstract Dysregulation of glutamate signaling is a core component of the pathological basis of drug addiction involving cocaine and many other substances. Recent progress in neuroscience and other fields clearly establishes that the molecular and cellular basis of glutamate-encoded signaling is vastly more complex than previously recognized. In particular, it is becoming increasingly evident that astrocytes, which are among the most abundant cells in the human brain, release glutamate to produce complex regulation over neural circuit activity. This novel form of glutamate-encoded intercellular signaling may be critical to understanding the pathological glutamate produced by long-term drug use since astrocytic glutamate release mechanisms, such as system xc- (Sxc), are altered by cocaine. While these discoveries raise numerous questions that may be essential in understanding glutamate signaling in the human brain, this proposal will focus on the question, how do neurons regulate glutamate release from astrocytes to control neural network activity and behaviors relevant to cocaine addiction. We will test the hypothesis that this is achieved by the actions of the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP), which we believe to be an unrecognized component of glutamate signaling in the nucleus accumbens (NAc). In support, we have found that A) PACAP mRNA is expressed in NAc afferents, B) PACAP receptors are expressed in NAc astrocytes and neurons projecting to the substantia nigra (SN) but not the ventral pallidum (VP), C) PACAP stimulates glutamate release from astrocytes by increasing the activity of system xc- (Sxc), D) PACAP application depresses eEPSCs in NAc medium spiny neurons (MSNs) projecting to the substantia nigra (SN) but not the ventral pallidum, and E) intra-NAc micro-infusion of PACAP blocks cocaine reinstatement. In this proposal, we will test the hypothesis that PACAP is a neuropeptide that regulates glutamate release from astrocytes and glutamate receptors on neurons to provide a novel form of pathway-specific regulation of NAc efferent pathways. In Aim 1, we will examine the molecular basis of PACAP-induced increases in Sxc activity and determine whether Sxc regulation is necessary for PACAP to depress eEPSCs in NAc-SN MSNs and block cocaine reinstatement. In this aim, we will also examine if PACAP increases glutamate from astrocytic release mechanisms other than Sxc. In Aim 2, we will examine the possibility that the form of astrocyte-neuron signaling triggered by PACAP require the regulation of neuronal glutamate receptors to produce the relevant changes in physiology that gate the output of NAc efferents and behavior. We will also explore whether PACAP alters presynaptic glutamate release. In Aim 3, we will investigate the role of endogenous PACAP to learn whether this neuropeptide is an unrecognized component of glutamate signaling in the NAc, and whether it is a key determinant of drug- seeking behavior.