Cholinergic Influences on Neuronal Physiology in Dorsolateral Prefrontal Cortex.

 描述（由申请人提供）：灵长类动物背外侧前额叶皮层（dlPFC）的锥体细胞微电路在精神分裂症中受到严重影响。对猴子的研究表明，这些回路通过树突棘上的NMDA受体（NMDAR）突触相互激发，产生工作记忆所需的持久神经表征。免疫电子显微镜显示烟碱-α7受体（nic- α 7 R）和毒蕈碱M1受体（M1 R）均位于突触后致密区（PSD）内的dlPFC谷氨酸突触中。在该基金的上一个任期内，我们发现nic-α 7 R的胆碱能刺激增强了灵长类dlPFC中的神经表征，并且允许NMDAR作用，从NMDAR阻断中拯救神经元放电。由于精神分裂症与NMDAR和nic-α 7 R信号传导受损相关，因此这些数据鼓励开发nic-α 7 R激动剂用于治疗PFC认知缺陷。然而，这种策略受到刺激后nic-α 7 R快速脱敏和外周nic-α 7 R药物作用的阻碍。因此，需要采取其他办法。刺激M1 R可能对dlPFC功能具有与nic-α 7 R类似的有益作用，并且可能提供更易处理的靶点，因为它们集中在与认知相关的脑区，但在外周神经系统中不那么普遍。由于精神分裂症与M1 R基因（CHRM 1）的变化和dlPFC中M1 R表达的减少有关，因此这些数据与该疾病的病因学和治疗直接相关。在拟议的研究中，目标1将检查M1 R的刺激是否像nic-α 7 R一样增强执行工作记忆任务的猴子中dlPFC神经元的放电，以及M1 R刺激是否允许NMDAR作用，如其突触定位所示。我们还将有机会测试一种新型的、高选择性的M1 R正变构调节剂（PAM），该调节剂由范德比尔特大学的Jeffrey Conn博士的药物发现小组创建，以观察这种化合物是否可以增强dlPFC神经元的放电，并改善猴子全身给药后的工作记忆。目的2将阐述M1 R在dlPFC中的作用机制，检查M1 R通过关闭KCNQ钾通道（Kv 7;也称为“M”通道）发挥作用的假设，KCNQ钾通道也位于第III层谷氨酸突触的PSD内，当被M1 R作用关闭时，定位为去突触膜并促进NMDAR信号传导。最后，目标3将测试对nic-α 7 R刺激做出反应的相同神经元是否也对M1 R做出反应，如果是，它们是否具有相加或协同相互作用。nic-α 7 R和M1 R刺激的叠加或协同作用可能导致联合治疗，允许更低的剂量，更少的副作用，绕过开发胆碱能治疗认知障碍的主要障碍。

 DESCRIPTION (provided by applicant): The pyramidal cell microcircuits of the primate dorsolateral prefrontal cortex (dlPFC) are gravely afflicted in schizophrenia. Research in monkeys has shown that these circuits excite each other through glutamatergic, NMDA receptor (NMDAR) synapses on dendritic spines to generate the persistent neural representations needed for working memory. Immunoelectron microscopy has revealed that both nicotinic-α7 receptors (nic- α7R), and muscarinic M1 receptors (M1R) are localized in dlPFC glutamate synapses within the post-synaptic density (PSD). During the previous tenure of this grant, we discovered that cholinergic stimulation of nic-α7R enhances neural representations in the primate dlPFC, and is permissive for NMDAR actions, rescuing neuronal firing from NMDAR blockade. As schizophrenia is associated with impaired NMDAR and nic-α7R signaling, these data encourage the development of nic-α7R agonists for the treatment of PFC cognitive deficits. However, this strategy has been hampered by the rapid desensitization of nic-α7R following stimulation, and by drug actions at peripheral nic-α7R. Thus, additional approaches are needed. Stimulation of M1R may have beneficial effects on dlPFC function similar to nic-α7R, and may provide a more tractable target since they are concentrated in brain areas relevant to cognition but are not as prevalent in the peripheral nervous system. As schizophrenia is associated with changes in the M1R gene (CHRM1) and with reduced M1R expression in dlPFC, these data have direct relevance to the etiology and treatment of this disease. In the proposed research, Aim 1 will examine whether stimulation of M1R, like nic-α7R, enhances the firing of dlPFC neurons in monkeys performing a working memory task, and whether M1R stimulation is permissive for NMDAR actions as suggested by their synaptic localization. We will also have the opportunity to test a novel, highly selective M1R positive allosteric modulator (PAM) created by Dr. Jeffrey Conn's Drug Discovery group at Vanderbilt University to see if this compound can enhance dlPFC neuronal firing and improve working memory following systemic administration in monkeys. Aim 2 will address the mechanism of M1R actions in dlPFC, examining the hypothesis that M1R act by closing KCNQ potassium channels (Kv7; also known as "M" channels), which are also localized within the PSD of layer III glutamate synapses, positioned to depolarize the synaptic membrane and facilitate NMDAR signaling when closed by M1R actions. Finally, Aim 3 will test whether the same neurons that respond to nic-α7R stimulation also respond to M1R, and if so, whether they have additive or synergistic interactions. Additive or synergistic actions of nic-α7R and M1R stimulation could lead to combined treatments that allow lower doses with fewer side effects, circumventing a major hurdle in the development of cholinergic therapeutics for cognitive disorders.