Neural mechanism underlying bladder contraction and relaxation : pressure-clamp method.

容量钳夹下膀胱呈大的排尿收缩-舒张节律。本研究通过阻断氯醛糖麻醉猫的膀胱内压，探讨了决定压力上限或触发松弛的神经机制。1.膀胱在低压钳下保持较恒定的容积，在高压钳下逐渐扩张。盆膀胱分支的传出神经在膀胱逐渐扩张时仍保持旺盛的放电。膀胱的扩张似乎与平滑肌纤维的结构有关，至少部分有关。2.在解剖了所有膀胱神经后，仍能观察到频率高达30次/min的膀胱流入-流出节律。在低压刺激下，盆腔传出神经活动呈节律性放电。然而，在较高的压力刺激，传出神经表现出没有明显的节律活动。看来，流入-流出节律最初是肌源性和/或膀胱和节后神经元之间的外周回路产生的，并且没有产生这种流动节律的中枢机制。3.在1000 mmH_2O以下，膀胱流入量随压力的增加而增加，传出神经放电频率随压力的增加而增加，但在一定压力以上，传出神经放电频率达到一个平台（P-plateau）。P-平台值几乎等于排尿收缩的最大压力，提示排尿收缩的上限由排尿中枢的饱和水平决定。4.在低压和高压钳下观察到传出活动的急剧减少，同时伴有间歇性的大流入，这表明中枢神经系统中存在抑制性神经机制。这似乎与排尿收缩后发生的舒张机制密切相关。

The bladder shows a large micturition contraction-relaxation rhythm under volume clamp. The present study examined the neural mechanisms determining the upper limit of the pressure or triggering the relaxation, by clamping an intravesical pressure of chloralose anesthetized cats. 1.The bladder kept fairly constant volume at low pressure-clamp, or gradually expanded at higher pressure-clamp. The efferent nerve of the pelvic bladder branch kept firing vigorously even while the bladder expanded gradually. Expansion of the bladder appeared to be related, at least partly, to the structure of smooth muscle fibers. 2.Inflow-outflow rhythm of the bladder with a high frequency (up to 30/min) was observed even after dissecting all bladder nerves. The efferent activities of the pelvic showed a rhythmic firing at lower pressure stimulation. At higher pressure stimulation, however, the efferent nerve showed no distinguishable rhythmic activities. It appeared that the inflow-outflow rhythm is originally generated myogenically and/or by the peripheral circuit between the bladder and the postganglionic neurones, and that there is no central mechanism generating this flow rhythm. 3.Inflow to the bladder increased as the clamped pressure was raised up to 1000 mmH_2O.The firing frequency of the efferent nerve also increased dependent on the clamped pressure, but it reached a plateau above a certain pressure (P-plateau). The value of P-plateau almost equaled the maximal pressure of micturition contraction, suggesting that the upper bound of micturition contraction is determined by the saturating level of the micturition center. 4.Dramatic decrease of the efferent activity concurrent with intermittent large inflows were observed at low pressure as well as high pressure-clamp, suggesting the existence of an inhibitory neural mechanism in the central nervous system. This appeared to be closely related to the relaxation mechanism occurring after micturition contraction.