NEUROSCIENCE

以往的研究表明，脑干的胆碱能投射神经元 脚桥核（PPN）调节黑质多巴胺（DA）神经元的兴奋性和放电频率。然而，乙酰胆碱（ACh）发挥其对DA细胞的影响的潜在机制尚不清楚。我们对胆碱能传入在调节DA细胞电活动中的作用感兴趣。具体来说，我们的目标是了解传入放电活动的变化与毒蕈碱受体激活阶段性（快速）和持续（强直）刺激的功能后果。假设与DA神经元激活相关的膜电位和钙动力学的变化受到快速（阶段性）和持续（强直性）毒蕈碱的不同调节。 受体刺激在急性分离的DA神经元中使用全细胞电压钳记录，将评估阶段性和强直性毒蕈碱应用（模拟PPN输出活性）对膜电位和细胞内钙动力学的影响。本研究将基于以下具体目的研究钙进入和从细胞内储存释放之间的相互作用：1）检测时相性毒蕈碱受体激活对全细胞膜电流和钙动力学的影响; 2）确定DA神经元响应毒蕈碱受体激活的钙升高幅度是否依赖于细胞内基础钙水平;（3）确定与DA神经元的毒蕈碱受体快速激活相关的第二信使机制。已知SNc DA活性高度受传入输入的调节，并且DA细胞对ACh的超极化和去极化反应之间的微妙平衡可能在SNc活性的调节中是关键的 和随后的DA递送到纹状体靶点。这项研究的发现可能对理解和开发运动和行为功能障碍的治疗方法具有重要意义。

Previous studies have demonstrated that cholinergic projection neurons from the brainstem pedunculopontine nucleus (PPN) modulate the excitability and firing rate of substantia nigra pars compacta (SNc) dopamine (DA) neurons. However, the underlying mechanisms by which acetylcholine (ACh) exerts its influence on DA cells remain unclear. We are interested in the role of cholinergic afferents in regulating DA cell electrical activity. Specifically, our goal is to understand the functional consequences of changes in afferent firing activity associated with muscarinic receptor activation during phasic (rapid) and sustained (tonic) stimulation. It is hypothesized that changes in membrane potential and calcium dynamics associated with DA neuron activation are differentially modulated by rapid (phasic) and sustained (tonic) muscarinic receptor stimulation. Using whole-cell voltage clamp recordings in acutely isolated DA neurons, the effects of phasic and tonic muscarine application (to mimic PPN output activity) on membrane potential and intracellular calcium dynamics will be assessed. The involvement of the interplay between calcium entry and release from intracellular stores will be investigated on the basis of the following specific aims: 1) To examine the effect of phasic muscarine receptor activation on whole-cell membrane currents and calcium dynamics; 2) to determine if the magnitude of the calcium rise in response to muscarinic receptor activation of DA neurons is dependent on basal intracellular calcium levels; and, 3) to determine the second messenger mechanisms associated with rapid muscarinic receptor activation of DA neurons. SNc DA activity is known to be highly regulated by afferent inputs and the delicate balance between the hyperpolarizing and depolarizing reponses of DA cells to ACh may be critical in the regulation of SNc activity and subsequent DA delivery to striatal targets. Findings from this study could have significant implications in understanding and developing treatments for movement and behavioral dysfunctions.