Functional connectome analysis of amphetamine action at dopamine neuron synapses

 描述(申请人提供)：精神刺激剂以多巴胺神经元为靶标，主要作用于多巴胺转运体。突触后纹状体回路中随后的动作既调节了对药物的急性行为反应，也调节了与成瘾相关的长期神经可塑性变化。大量的工作集中在多巴胺的释放和多巴胺的作用上，但直到最近随着光遗传学的出现，多巴胺神经元的突触作用才变得可以直接研究。光遗传学使一种功能连接组方法能够确定多巴胺神经元的突触活动。在这种方法中，通道视紫红质2在已识别的神经元群体中全面表达，并通过测量该神经元群体与已识别的靶神经元的连接总数来确定功能连接指数，该指数包括连接的发生率及其强度。确定纹状体棘突投射神经元的功能连接体--多巴胺神经元的主要突触后目标--提供了功能连通性的定量测量，超越了解剖学数据，直接测量突触强度。虽然棘突投射神经元似乎只通过GABA发出信号，但多巴胺神经元通过多巴胺以及谷氨酸和GABA发出信号，并以不同纹状体区域的纹状体神经元为靶标。多巴胺能神经元与腹侧纹状体的胆碱能中间神经元建立强大的谷氨酸能突触联系，特别是伏隔核的内侧壳，它似乎是介导苯丙胺急性行为反应的关键因素。一次小剂量的苯丙胺，产生运动刺激，显著和选择性地减弱这些谷氨酸能联系。相比之下，高剂量的苯丙胺会导致刻板的行为，广泛地减弱纹状体中的多巴胺能联系。这支持了一种假设，即苯丙胺诱导的特定群体多巴胺神经元突触的可塑性是驱动纹状体的关键 通向上瘾状态的电路。为了解决这一假设，三个具体的目标是：确定纹状体中的多巴胺神经元功能连接体，绘制纹状体中多巴胺神经元的突触活动图。确定苯丙胺如何在一次暴露后调节多巴胺神经元功能连接体，检查区域异质性，以及调节的时机和持久性。&lt；3&gt；确定最受影响的连接的作用，作为苯丙胺回路和行为影响的关键中介。用功能连接组的术语表达苯丙胺诱导的作用，使系统的突触-电路-行为方法能够阐明苯丙胺作用的突触底物和成瘾的开始。

 DESCRIPTION (provided by applicant): Psychostimulants target dopamine neurons, acting principally at the dopamine transporter. Ensuing actions in the postsynaptic striatal circuitry mediate both the acute behavioral response to the drug as well as longer-term neuroplastic changes associated with addiction. Extensive work has focused on dopamine release and on the actions of dopamine, but only recently with the advent of optogenetics have dopamine neuron synaptic actions become directly accessible to study. Optogenetics enables a functional connectome approach to determining dopamine neuron synaptic actions. In this approach, channelrhodopsin 2 is expressed comprehensively in an identified population of neurons and the sum total of the connections of the population of neurons onto identified target neurons measured to determine a functional connectivity index comprising the incidence of connections and their strength. Determining the functional connectome of striatal spiny projection neurons - the principal postsynaptic targets of dopamine neurons - has provided quantitative measures of functional connectivity, going beyond anatomical data to direct measures of synaptic strength. While spiny projection neurons appear to signal solely via GABA, dopamine neurons signal via dopamine as well as glutamate and GABA, and differentially target striatal neurons in different striatal regions. Dopamine neurons make robust glutamatergic synaptic connections with cholinergic interneurons in the ventral striatum, specifically in the medial shell of the nucleus accumbens that appear to be critically involved in mediating the acute behavioral response to amphetamine. A single low dose of amphetamine, which engenders motoric stimulation, significantly and selectively attenuates these glutamatergic connections. In contrast, a high amphetamine dose, which engenders stereotypic behavior, broadly attenuates dopaminergic connections throughout the striatum. This motivates the hypothesis that amphetamine-induced plasticity of specific populations of dopamine neuron synapses is critical for driving the striatal circuitry towards the addicted state. To address this hypothesis, the three specific aims are to: <1> Determine the dopamine neuron functional connectome in the striatum, mapping the synaptic actions of dopamine neurons across the striatum. <2> Determine how amphetamine modulates the dopamine neuron functional connectome following a single exposure, examining regional heterogeneity, and the timing and persistence of the modulation. <3> Determine the role of the most affected connections, as crucial mediators of amphetamine circuit and behavioral effects. Expressing amphetamine-induced actions in functional connectome terms enables a systematic synapses-to-circuits-to-behavior approach to elucidating the synaptic substrate of amphetamine action and the inception of addiction.