Kamo Izumi, Kaiho Yasuhiro, Miyazato Minoru, Torimoto Kazumasa, Yoshimura Naoki
Departments of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA.
Low Urin Tract Symptoms. 2009 Sep 1;1(s1):S40-S43. doi: 10.1111/j.1757-5672.2009.00026.x.
Urethral closure mechanisms during abrupt elevation of intravesical pressure (P(ves)) were investigated. During sneezing, the middle urethral closing response was observed and it still remained after opening the abdomen. The middle urethral response was almost completely abolished after bilateral transection of somatic nerves innervating the external urethral sphincter and the pelvic floor muscles, while bilateral transection of both pelvic nerves and hypogastric nerves had no effects. Somatic nerve transection resulted in fluid leakage from the urethral orifice during sneezing. Passive increments of P(ves) for 120 seconds by elevating a saline reservoir connected to the bladder also induced the middle urethral closing response in rats with spinal cord transection at T8-T9. The response was totally abolished by cutting pelvic nerves bilaterally, and partially reduced after bilateral transection of pudendal nerves, nerves to pelvic floor muscles or hypogastric nerves. Electrical stimulation of abdominal muscles (ESAM) for 1 second elevated P(ves) in a stimulus-dependent manner in the spinal cord-transected rats, and the P(ves) rise was almost lost when the abdomen was opened. The P(ves) inducing fluid leakage from the urethral orifice was lowered in rats when pelvic nerves or somatic nerves were cut bilaterally, while transection of bilateral hypogastric nerves showed smaller effects. These results indicate that at least two kinds of urinary continence reflexes close the middle urethra during abrupt elevation of P(ves); one reflex observed during sneeze is preprogrammed so as to close the urethra automatically irrespective of bladder afferent activity, and the other reflex is triggered by bladder afferent excitation. During momentary stress events such as sneezing (<0.15 seconds) and ESAM (1 second), the striated muscles mainly contribute to the urethral closure, while during events for a relatively long period like passive P(ves) elevation for 120 seconds, both striated and smooth muscles are involved in the prevention of stress urinary incontinence.
研究了膀胱内压（P(ves)）突然升高时的尿道闭合机制。在打喷嚏时，观察到尿道中段的闭合反应，并且在打开腹腔后该反应仍然存在。在双侧切断支配尿道外括约肌和盆底肌肉的躯体神经后，尿道中段反应几乎完全消失，而双侧切断盆神经和腹下神经则没有影响。躯体神经切断导致打喷嚏时尿道口漏液。通过升高连接膀胱的盐水储液器使P(ves)被动增加120秒，也可在T8 - T9脊髓横断的大鼠中诱发尿道中段闭合反应。双侧切断盆神经可使该反应完全消失，而双侧切断阴部神经、支配盆底肌肉的神经或腹下神经后，反应部分减弱。在脊髓横断的大鼠中，电刺激腹肌（ESAM）1秒以刺激依赖的方式升高P(ves)，当打开腹腔时，P(ves)的升高几乎消失。当双侧切断盆神经或躯体神经时，大鼠中导致尿道口漏液的P(ves)降低，而双侧切断腹下神经的影响较小。这些结果表明，在P(ves)突然升高时，至少有两种尿失禁反射可闭合尿道中段；一种在打喷嚏时观察到的反射是预先编程的，以便无论膀胱传入活动如何都能自动闭合尿道，另一种反射由膀胱传入兴奋触发。在打喷嚏（<0.15秒）和ESAM（1秒）等瞬间应激事件期间，横纹肌主要有助于尿道闭合，而在被动升高P(ves) 120秒等相对较长时间的事件期间，横纹肌和平滑肌都参与预防压力性尿失禁。
