Kruse M N, Mallory B S, Noto H, Roppolo J R, de Groat W C
Department of Pharmacology, University of Pittsburgh, PA 15261.
Brain Res. 1991 Aug 9;556(1):6-12. doi: 10.1016/0006-8993(91)90541-3.
The micturition reflex is thought to be mediated by a spinobulbospinal reflex pathway passing through the rostral pons. This study examined the properties of the descending limb of the reflex pathway by monitoring the responses of the lower urinary tract to stimulation of the pons in the decerebrate cat. Electrical stimulation (300 microseconds pulses at 50 Hz intratrain frequencies, 300-500 ms trains, 0.5-15 V) in the region of the locus coeruleus (P 0.5-3.1/L 2-4/H to -2.75) was used to activate the descending excitatory pathway to the sacral parasympathetic nucleus. Low intensity stimulation induced small amplitude, short duration (14 +/- 11 cm H2O, 10 +/- 3 s) bladder contractions in a partially full bladder, whereas higher intensity stimulation induced large amplitude, long duration (69 +/- 29 cm H2O, 70 +/- 44 s) contractions which were similar to distension-induced reflex micturition contractions. The evoked bladder contractions coincided with a reduction in external urethral sphincter (EUS) EMG activity. Following bilateral L7-S3 dorsal root transection, electrical stimulation of the pons still elicited the small amplitude bladder contractions, but the larger amplitude, long duration micturition contractions were abolished. During these small evoked bladder contractions, a suppression of EUS activity still occurred following deafferentation, indicating a pontine mediated bladder/EUS synergy. It is concluded that the pons can initiate bladder contractions and coordinated bladder-sphincter activity, but that afferent feedback (via the dorsal roots) is needed to maintain the large amplitude micturition contractions.
排尿反射被认为是由一条经过脑桥嘴侧的脊髓-延髓-脊髓反射通路介导的。本研究通过监测去大脑猫下尿路对脑桥刺激的反应，来研究该反射通路下行支的特性。在蓝斑区域（P 0.5 - 3.1/L 2 - 4/H至 - 2.75）进行电刺激（50 Hz串内频率的300微秒脉冲，300 - 500毫秒串，0.5 - 15伏），以激活至骶副交感核的下行兴奋性通路。低强度刺激在膀胱部分充盈时诱发小幅度、短持续时间（14±11 cmH₂O，10±3秒）的膀胱收缩，而高强度刺激则诱发大幅度、长持续时间（69±29 cmH₂O，70±44秒）的收缩，这与扩张诱发的反射性排尿收缩相似。诱发的膀胱收缩与尿道外括约肌（EUS）肌电图活动的降低同时出现。双侧L7 - S3背根横断后，脑桥电刺激仍能诱发小幅度膀胱收缩，但大幅度、长持续时间的排尿收缩消失。在这些小幅度诱发的膀胱收缩期间，去传入神经后EUS活动仍受到抑制，表明存在脑桥介导的膀胱/EUS协同作用。结论是，脑桥可引发膀胱收缩和协调膀胱-括约肌活动，但需要传入反馈（通过背根）来维持大幅度排尿收缩。
