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）和膀胱过动症（OAB）是慢性泌尿系统疾病，其特征是尿急和排尿频率增加。将IC与OAB区分开来的一个决定性特征是存在骨盆/耻骨上疼痛，并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），并且有害的内脏刺激不同于有害的皮肤刺激，因此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患者所经历的症状的基础。然而，由于每个队列的症状定义组合（有或没有疼痛的急迫性和频率）不同，并且由于症状来自膀胱传入的共同全球群体，因此转导的选择性改变必须发生在传入亚群内，或在传入亚群所参与的中枢通路中，或两者兼有。人们对这些现象知之甚少。具有轻度髓鞘或无髓鞘外周纤维的异质膀胱神经元亚群(A？-和c -纤维分别)传递有关多个过程的信息，包括稳态监测（代谢受体）和检测潜在的破坏性刺激（伤害感受器）。有些纤维表现出化学敏感性，大多数纤维对机械刺激有反应，尽管有些纤维仅在病理条件下才获得机械敏感性。我们建议在膀胱传入事件的特定亚群中使用表达光门控离子通道，通道视紫红质-2 （ChR2）的转基因小鼠系，以解决它们各自对IC和OAB主要症状的贡献。我们假设膀胱传入的亚群对排尿过程和伤害感觉有独特的贡献。我们将通过研究传入亚群的贡献来验证这一假设：1)使用离体制备来功能性评估内在和机械，化学和光诱发反应特征，2)体内排尿和伤害反射的表达，以及3)脊髓不同区域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.