老年特发性低活动膀胱（UAB）外周感觉神经机制的实验研究

Underactive bladder (UAB) or detrusor underactivity (DU) is a poorly understood, common bladder dysfunction for which no effective therapies are available. UAB will become a top priority in urology research over the next decades. Animal as well as human studies provided evidence suggesting diminished afferent activity contributes to the pathogenesis of idiopathic UAB (no neurogenic no obstructive). However, the underling neural mechanisms for diminished afferent activity are not yet clear. We found that old female rats (retired breed mom) have the similar voiding behavior with old idiopathic UAB patients, they exhibit a reduced bladder response to intravesically application of 1µM capsaicin ( TRPV1 agonist ) as well as 20 nM GSK1016790A (a TRPV4 agonist). We hypothesize that reduction in the excitability and TRPV1 or TRV4 activities in bladder primary sensory neurons are the two important underling mechanisms for the diminished afferent activity and therefore the pathogenesis of UAB. To test this hypothesis, whole cell patch clamp as well as Ca2+ imaging technique will be performed in dorsal root ganglion (DRG) neurons that innervates the bladder. Our study try to prove our hypothesis with the following experiments：（1）Passive and active electrophysiological properties particularly the excitability will be examined in bladder DRG neurons from old female rats (2) voltage gated Na+ or K+ channel properties including activation, inactivation and deactivation will be evaluated in bladder DRG neurons from old female rats; (3) TRPV1 or TRPV4 channels activities including agonist evoked inward currents and the Ca2+ influx will be examined in bladder DRG neurons from old female rats; (4) test whether decrease of estrogen level facilitate the pathogenesis of UAB. Elucidation of these mechanisms will provide the candidate channels such as TRPV4 for UAB treatment.

低活动膀胱（UAB）或逼尿肌无力（DU）无有效的药物治疗手段，是今后几十年泌尿界的重要研究课题。国际上普遍认为膀胱感觉传入障碍是特发性UAB的一个重要病理生理机制，但导致感觉传入障碍的外周神经分子机制还不清楚。我们发现多次生育后老年雌性大鼠的排尿行为与UAB病人相似，而且感觉功能降低，表现为排尿反射的容积及压力阈值增高，对辣椒素刺激的反应降低。我们假设：膀胱初级感觉神经元（DRG）兴奋性的降低和其表达的TRPV1、TRPV4通道功能的降低导致了感觉传入减弱和UAB的发生，我们将以膜片钳和钙离子成像技术，以老年大鼠膀胱DRG神经元为研究对象，从以下几方面验证上述假设：（1）观察神经元电生理特性特别是兴奋性的改变；（2）电压依赖性Na+或K+通道功能的改变；（3）TRPV1或TRPV4通道功能的改变；（4）雌激素水平的降低对UAB的促进作用。该研究将帮助找到治疗UAB药物的分子靶点。

低活动膀胱（UAB）或逼尿肌无力（DU）无有效的药物治疗手段，是今后几十年泌尿界的重要研究课题。国际上普遍认为膀胱感觉传入障碍是特发性UAB的一个重要病理生理机制，但导致感觉传入障碍的外周神经分子机制还不清楚。我们以生育淘汰的老年雌性大鼠（鼠龄≥12个月）为研究对象，通过行为学，电生理、钙离子成像及分子生物学等技术，观察比较了老年大鼠与成年大鼠（鼠龄2-3个月）的排尿行为、TRPV4及TRPV1膀胱机械感受性的表达以及支配膀胱初级感觉神经元兴奋性的差别。我们发现：①老年雌性大鼠储尿期感觉功能降低及排尿反射的压力及容积阈值增大；②老年大鼠对膀胱内灌注TRPV4的激动剂GSK及TRPV1的激动剂辣椒素的反应减弱；③老年大鼠膀胱粘膜上皮对TRPV4的激动剂GSK诱发的胞内钙离子幅度降低，同时TRPV4的蛋白表达降低；④支配老年大鼠的初级感觉神经元对TRPV1的激动剂辣椒素诱发的胞内钙离子升高幅度降低，诱发的内向电流幅度下降；⑤支配老年大鼠的初级感觉神经元的电生理学特性特别是兴奋性降低；⑥老年大鼠TRPV4的激动剂GSK膀胱内灌注，可以降低排尿间隔，增强膀胱排尿期逼尿肌的压力，改善排尿效率。本研究的完成为老年特发性UAB发生机制的研究建立了一个模型。揭示了膀胱初级感觉神经机制的改变在老年特发性UAB发生中的重要作用，提出初级感觉神经元兴奋性的降低以及膀胱粘膜上皮TRPV4功能的降低可能是老年特发性UAB产生的重要分子机制。为充分认识UAB的发病机制及开发治疗UAB的药物提供了分子靶点。为最终找到治愈UAB的药物提供坚实的研究基础。TRPV4的激动剂可能成为治疗老年特发性UAB的药物，此模型也可作为筛选其它可能有效治疗UAB药物的工具。