Optogenetic dissection of the functional properties of bladder afferent populations

描述(由申请人提供)：间质性膀胱炎(IC)和膀胱过度活动症(OAB)是以尿急和尿频增加为特征的慢性泌尿系统疾病。IC区别于OAB的一个明显特征是存在骨盆/耻骨上疼痛，随着疾病的进展而加重。由于内脏神经的独特性(器官由两条神经支配)和伤害性内脏刺激不同于伤害性皮肤刺激，膀胱过敏的机制不同于皮肤痛觉过敏。膀胱的机械和/或化学过敏在很大程度上是IC和OAB患者症状的基础。然而，由于每个队列的症状(有或无疼痛的紧迫感和频率)的定义组合不同，而且症状产生于全球共同的膀胱传入人群，因此信号转导必须发生选择性变化，要么发生在传入亚群中，要么发生在传入亚群参与的中央通路中，或者两者兼而有之。人们对这些现象知之甚少。具有轻度有髓或无髓外周纤维(分别为A？纤维和C-纤维)的异质膀胱神经元亚群传递有关多个过程的信息，包括稳态监测(代谢物受体)和检测潜在的破坏性刺激(伤害性感受器)。有些纤维表现出化学敏感性，大多数对机械刺激有反应，尽管有些纤维可能只在病理条件下获得机械敏感性。我们建议使用在特定的膀胱传入亚群中表达光门离子通道通道视紫红质-2(ChR2)的转基因小鼠来研究它们在IC和OAB主要症状中的各自作用。我们假设，膀胱传入的亚群对排尿过程和伤害性感觉有独特的贡献。我们将通过研究传入亚群的贡献来验证这一假设：1)使用体外准备来从功能上评估内在的和机械的、化学的和光诱发的反应特征，2)对体内排尿和伤害性反射的表达，以及3)对接受膀胱传入的神经元在脊髓不同区域的激活。

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.