Role of astrocytes in dopamine signaling and psychostimulant effects

多巴胺（DA）信号传导涉及大量的大脑功能，包括运动控制、学习和认知功能。 记忆和奖励它受到精神兴奋剂安非他明和可卡因的影响， 通过增加细胞外DA水平发挥作用。与神经元的广泛研究相反， 星形胶质细胞在DA信号传导和精神兴奋作用中的参与仍然在很大程度上未被探索。 星形胶质细胞在脑功能中起支持作用，它们还可以影响神经元和突触 通过与三重突触中的神经元的双向通讯进行活动。星形胶质细胞反应 与钙升高的几种神经递质（如谷氨酸，乙酰胆碱，或 内源性大麻素），并释放调节突触传递的神经胶质递质。但无论 星形胶质细胞对DA反应并因此调节神经传递仍然是未知的。 目前的建议旨在确定星形胶质细胞参与DA信号在核 大脑皮层（NAc），一个涉及奖励和成瘾的边缘系统区域，并确定星形胶质细胞 有助于精神兴奋剂安非他明的作用。我们假设星形胶质细胞参与了 在NAc中DA信号传导的细胞机制和功能后果中， 因此，它们有助于安非他明的突触效应。我们的初步结果表明， DA激活NAc中的星形胶质细胞，从而刺激神经胶质递质腺苷的释放， 调节兴奋性突触传递。目前的建议将：1）定义细胞机制 基础DA控制NAc中星形胶质细胞活性; 2）确定DA介导的 星形胶质细胞活动对突触传递的影响; 3）确定安非他明对星形胶质细胞和突触传递的作用。 活性和星形胶质细胞介导的突触调节。 我们将使用最先进的技术，包括药物遗传学（“设计受体专门 由设计药物激活”，DREADD），光遗传学选择性刺激多巴胺能轴突， 同步双光子Ca 2+成像和电生理记录，和转基因小鼠。 预期的结果将揭示星形胶质细胞作为参与DA信号传导的细胞成分，从而有助于 安非他明的影响。他们将在细胞内确定NAc中的星形胶质细胞-神经元相互作用。 水平，为未来的研究铺平了道路，认识到星形胶质细胞作为参与相关行为的元素 奖励和精神兴奋剂如果星形胶质细胞参与多巴胺信号传导，而星形胶质细胞- 神经元通信受到精神兴奋剂的影响，这将揭示新的机制， 作为动机障碍如药物成瘾的治疗靶点。

Dopamine (DA) signaling is involved in a plethora of brain functions, including motor control, learning and memory, and reward. It is affected by the psychostimulants amphetamine and cocaine, which are thought to act by increasing the extracellular DA levels. In contrast to the extensive studies in neurons, the involvement of astrocytes in DA signaling and psychostimulant actions remain largely unexplored. Astrocytes play supportive roles in brain function, and they can also influence neuronal and synaptic activity through the bidirectional communication with neurons in tripartite synapses. Astrocytes respond with calcium elevations to several neurotransmitters (such as glutamate, acetylcholine, or endocannabinoids), and release gliotransmitters that modulate synaptic transmission. However, whether astrocytes respond to DA and consequently regulate neurotransmission remain largely unknown. The present proposal aims to define the involvement of astrocytes in DA signaling in the nucleus accumbens (NAc), a limbic area implicated in reward and addiction, and to identify the astrocyte contribution to the actions of the psychostimulant amphetamine. We hypothesize that astrocytes participate in the cellular mechanisms and functional consequences of DA signaling in the NAc and, as a consequence, they contribute to the synaptic effects of amphetamine. Our preliminary results indicate that DA activates astrocytes in the NAc, which stimulates the release of the gliotransmitter adenosine that regulates excitatory synaptic transmission. The present proposal will: 1) define the cellular mechanisms underlying DA control of the astrocyte activity in the NAc; 2) determine the consequences of DA-mediated astrocyte activity on synaptic transmission; 3) determine the actions of amphetamine on both astrocytic activity and astrocyte-mediated synaptic regulation. We will use state-of-the-art techniques, including pharmacogenetics (“designer receptors exclusively activated by designer drugs”, DREADDs), optogenetics to selectively stimulate dopaminergic axons, simultaneous two-photon Ca2+ imaging and electrophysiological recordings, and transgenic mice. The expected results will reveal astrocytes as cellular elements involved in DA signaling, thus contributing to the effects of amphetamine. They will define the astrocyte-neuron interactions in the NAc at the cellular level, paving the way for future studies recognizing astrocytes as elements involved in behaviors associated with reward as well as psychostimulant drugs. If astrocytes are involved in DA signaling, and astrocyte- neuron communication is affected by psychostimulants, this will reveal novel mechanisms that may serve as therapeutic targets in motivation disorders such as drug addiction.