The goal of this study in anesthetized cats was to identify silent hypogastric nerve (HGN) afferent fibers that do not respond to bladder distention but become responsive after chemical irritation of the bladder. The HGN was split into multiple filaments small enough for recording action potentials from single or multiple afferent fibers. The bladder was distended by infusion of either saline or 0.5% acetic acid (AA) through a urethral catheter while recording intravesical pressure. A total of 90 HGN filaments from 17 cats responded to bladder distention with saline or AA. Three types of HGN afferents were identified. The first type was non-nociceptive mechano-sensitive that responded to bladder distention at normal physiological pressures (10-40 cmH2O). The second type was nociceptive mechano-sensitive that only responded to high-pressure (50-80 cmH2O) bladder distention with saline but responded to low-pressure bladder distention after sensitization with AA. The third type was chemo-sensitive nociceptive that was silent even during high-pressure bladder distention but after sensitization with AA did respond to low-pressure bladder distention. These results indicate that HGN afferents as well as pelvic nerve afferents may play a role in bladder nociception. The HGN afferent fibers that are silent during bladder distention at normal physiological pressures but become responsive after chemical irritation are important for understanding the possible pathophysiological mechanism underlying bladder allodynia in painful bladder syndrome.

中文翻译：

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下胃传入纤维对猫膀胱扩张或刺激的反应。

这项在麻醉猫中进行的研究的目的是鉴定对膀胱扩张无反应但在对膀胱进行化学刺激后变得有反应的无声下腹神经（HGN）传入纤维。HGN被分成多根细丝，细丝足以记录单根或多根传入纤维的动作电位。在记录膀胱内压力的同时，通过尿道导管输注盐水或0.5％乙酸（AA）使膀胱扩张。来自17只猫的90条HGN细丝对盐水或AA引起的膀胱扩张有反应。确定了三种类型的HGN传入。第一类是非伤害性机械敏感，在正常生理压力（10-40 cmH2O）下对膀胱扩张有反应。第二种是伤害性机械敏感型，仅对高压（50-80 cmH2O）的膀胱扩张用生理盐水有反应，而对AA致敏后的低压膀胱扩张有反应。第三类是对化学敏感的伤害感受，即使在高压膀胱扩张期间也没有表现出来，但是用AA致敏后确实对低压膀胱扩张有反应。这些结果表明HGN传入以及盆腔神经传入可能在膀胱伤害感受中起作用。HGN传入纤维在正常生理压力下的膀胱扩张期间无声，但在化学刺激后变得反应灵敏，对于了解疼痛性膀胱综合征中膀胱异常性疼痛的可能病理生理机制非常重要。