Functional connectome analysis of amphetamine action at dopamine neuron synapses

 描述（由申请人提供）：精神兴奋剂以多巴胺神经元为目标，主要作用于多巴胺转运蛋白。突触后纹状体回路中的后续作用介导对药物的急性行为反应以及与成瘾相关的长期神经塑性变化。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，多巴胺神经元突触作用才变得可以直接研究。光遗传学使得功能性连接体方法能够确定多巴胺神经元突触作用。在该方法中，视紫红质通道蛋白2在已识别的神经元群体中全面表达，并且测量该神经元群体与已识别的目标神经元的连接总数，以确定包括连接发生率及其强度的功能连接指数。确定纹状体棘投射神经元（多巴胺神经元的主要突触后目标）的功能连接组提供了功能连接的定量测量，超越了解剖数据，直接测量了突触强度。虽然多刺投射神经元似乎仅通过 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目标。多巴胺神经元与腹侧纹状体中的胆碱能中间神经元建立强大的谷氨酸能突触连接，特别是在伏隔核的内侧壳中，伏隔核的内侧壳似乎与介导对安非他明的急性行为反应至关重要。单次低剂量的安非他明会产生运动刺激，显着且选择性地减弱这些谷氨酸能连接。相反，高剂量的安非他明会产生刻板行为，广泛削弱整个纹状体的多巴胺能连接。这激发了这样的假设：安非他明诱导的特定多巴胺神经元突触群体的可塑性对于驱动纹状体至关重要。 电路走向成瘾状态。为了解决这一假设，三个具体目标是：<1>确定纹状体中的多巴胺神经元功能连接组，绘制纹状体中多巴胺神经元的突触作用。 <2> 确定单次暴露后安非他明如何调节多巴胺神经元功能连接组，检查区域异质性以及调节的时间和持久性。 <3> 确定受影响最大的连接的作用，作为安非他明回路和行为影响的关键介质。用功能连接组术语表达安非他明诱导的作用，可以采用系统的突触到电路到行为的方法来阐明安非他明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.