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

膀胱在容量钳下表现出较大的排尿收缩-放松节律。本研究通过对氯氯蔗糖麻醉的猫施加膀胱内压力，研究了决定压力上限或触发放松的神经机制。1.在低压夹持下，膀胱体积基本保持恒定，在高压夹持下，膀胱体积逐渐膨胀。在膀胱逐渐扩张的同时，盆腔膀胱分支的传出神经仍保持强烈的放电。膀胱的扩张似乎至少部分与平滑肌纤维的结构有关。2.即使在解剖所有膀胱神经后，仍观察到膀胱高频率的流入-流出节律（高达30/min）。盆腔的传出活动在低压刺激下表现出有节奏的放电。然而，在高压刺激下，传出神经没有明显的节律性活动。似乎流入-流出节律最初是由肌源性和/或由膀胱和神经节后神经元之间的外周电路产生的，并且没有中枢机制产生这种流动节律。3.当夹持压力提高到1000 mmH_2O时，膀胱的流入增加。传出神经的放电频率也随夹紧压力的增加而增加，但在一定压力以上达到平台（p -平台）。p -平台值几乎等于排尿收缩的最大压力，说明排尿收缩的上限是由排尿中心的饱和水平决定的。4.在低压和高压夹持下，传出活动在间歇性大流量流入的同时显著减少，提示中枢神经系统中存在抑制神经机制。这似乎与排尿收缩后的松弛机制密切相关。

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.