Optogenetic dissection of the functional properties of bladder afferent populations

描述（由申请方提供）：间质性膀胱炎（IC）和膀胱过度活动症（OAB）是以尿急和排尿频率增加为特征的慢性泌尿系统疾病。IC区别于OAB的一个定义性特征是盆腔/耻骨上疼痛的存在，随着疾病的进展而加重。由于内脏神经支配是独特的（器官由两条神经支配），并且伤害性内脏刺激不同于伤害性皮肤刺激，因此膀胱超敏反应的机制不同于皮肤痛觉过敏的机制。膀胱的机械和/或化学超敏反应在很大程度上是IC和OAB患者所经历的症状的基础。然而，由于每个队列的症状（尿急和尿频伴或不伴疼痛）的定义组合不同，并且由于症状来自共同的全球膀胱传入神经群体，因此转导的选择性变化必须发生在传入神经亚群内，或传入神经亚群参与的中枢通路之间，或两者兼而有之。人们对这些现象知之甚少。具有轻度有髓或无髓外周纤维的异质性膀胱神经元亚群（A？- 和C-纤维）传递关于多个过程的信息，包括稳态监测（代谢感受器）和潜在损害性刺激的检测（伤害感受器）。一些纤维表现出化学敏感性，大多数对机械刺激有反应，尽管有些纤维可能仅在病理条件下获得机械敏感性。我们建议使用转基因小鼠系表达的光门控离子通道，通道视紫红质-2（ChR 2），在特定的子集的膀胱传入，以解决各自的贡献IC和OAB的主要症状。我们假设膀胱传入神经的亚群对排尿过程和伤害性感受有独特的作用。我们将通过研究传入亚群的贡献来测试这一假设：1）使用离体制备物来功能性地评估内在和机械、化学和光诱发的反应特征，2）体内排尿和伤害性反射的表达，以及3）脊髓不同区域中接受膀胱传入输入的神经元的激活。

DESCRIPTION (provided by applicant): Interstitial cystitis (IC) and overactive bladder (OAB) are chronic urological disorders characterized by urinary urgency and increased micturition frequency. A defining characteristic of IC that distinguishes it from OAB is the presence of pelvic/suprapubic pain that worsens as the disease progresses. Because visceral innervation is unique (organs are innervated by two nerves) and noxious visceral stimuli are unlike noxious cutaneous stimuli, mechanisms of bladder hypersensitivity differ from those of cutaneous hyperalgesia. Mechanical and/or chemical hypersensitivity of the bladder largely underlies the symptoms experienced by both IC and OAB patients. Yet, because the defining combination of symptoms (urgency and frequency with or without pain) for each cohort differs, and because symptoms arise from a common global population of bladder afferents, selective changes in transduction must occur either within afferent subpopulations, or among the central pathways engaged by afferent subpopulations, or both. These phenomena are poorly understood. Heterogeneous bladder neuronal subpopulations with lightly myelinated or unmyelinated peripheral fibers (A? - and C-fibers, respectively) convey information about multiple processes, including homeostatic monitoring (metaboreceptors) and detection of potentially damaging stimuli (nociceptors). Some fibers exhibit chemosensitivity, and most respond to mechanical stimuli, although some may acquire mechanosensitivity only during pathological conditions. We propose to use transgenic mouse lines expressing the light-gated ion channel, channelrhodopsin-2 (ChR2), in specific subsets of bladder afferents to address their respective contributions to the cardinal symptoms of IC and OAB. We hypothesize that subpopulations of bladder afferents contribute uniquely to micturition processes and nociception. We will test this hypothesis by studying afferent subpopulation contributions: 1) using an ex vivo preparation to functionally evaluate intrinsic and mechanical, chemical, and light-evoked response characteristics, 2) to the expression of in vivo micturition and nociceptive reflexes, and 3) to th activation of neurons receiving bladder afferent input in distinct regions of the spinal cord.