PACAP-Dependent Coordination of Glutamate Signaling between Neurons and Astrocytes

项目概要/摘要 谷氨酸信号转导失调是药物成瘾病理基础的核心组成部分， 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，这是其中最重要的 人类大脑中丰富的细胞释放谷氨酸盐，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理解病理性 谷氨酸产生的长期药物使用，因为星形胶质细胞谷氨酸释放机制，如系统 xc-（Sxc），被可卡因改变。虽然这些发现提出了许多问题， 了解谷氨酸信号在人脑中，这个建议将集中在这个问题上，如何做 神经元调节从星形胶质细胞释放谷氨酸，以控制神经网络活动和行为， 可卡因成瘾我们将检验这是通过脑垂体神经肽的作用实现的假设 腺苷酸环化酶激活多肽（PACAP），我们认为这是一个未被认识的组成部分， 谷氨酸信号传导在脑桥核（NAc）。作为支持，我们发现A）PACAP mRNA是 B）PACAP受体在NAc星形胶质细胞和投射到 C）PACAP刺激黑质（SN）而非腹侧苍白球（VP）的谷氨酸释放， D）PACAP应用抑制NAc中的eEPSC 中棘神经元（MSNs）投射到黑质（SN），但不投射到腹侧苍白球，和E） NAc内微量输注PACAP阻断可卡因复吸。在本提案中，我们将检验假设 PACAP是一种神经肽，调节星形胶质细胞和谷氨酸受体释放谷氨酸， 神经元提供了一种新的形式的途径特异性调节NAc传出途径。在目标1中，我们 检查PACAP诱导的Sxc活性增加的分子基础，并确定Sxc是否 调节对于PACAP抑制NAc-SN MSN中的eEPSC和阻断可卡因复吸是必要的。在 为此，我们还将研究PACAP是否通过星形胶质细胞释放机制增加谷氨酸， SXC。在目标2中，我们将研究由PACAP触发的星形胶质细胞-神经元信号传导形式的可能性。 需要调节神经元谷氨酸受体，以产生相关的生理变化， NAc传出神经和行为的输出。我们还将探讨PACAP是否改变突触前谷氨酸 release.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神经递质。 NAc中谷氨酸信号传导的未识别成分，以及它是否是药物作用的关键决定因素， 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.