Role of the spinal neural mechanism controlling the micturition in conjunction with descending pathways from Barrington's nucleus

巴林顿核，或桥脑排尿中心，已被证明直接投射到支配膀胱肌的神经节前神经元，使用神经元追踪技术。我们用电生理学技术研究了该核团是否与麻醉猫的骶管节前神经元直接相连。用神经节前神经元作细胞内记录。当膀胱压力较低时，单次至三次电击Barrington核可在节前神经元内诱发出无或微弱的EPSP。事实上，巴灵顿核需要30-50个脉冲的刺激才能引起膀胱收缩。另一方面，单次电击Barrington核后，在排尿期可诱发出清晰的EPSP。所有节前神经元的EPSP潜伏期均不固定，表明EPSP是以多突触方式诱发的。进一步研究了Barrington核和膀胱传入的相互作用。电气…更多的盆腔传入刺激在支配膀胱的骶神经节前神经元上诱发出潜伏期较短的IPSP。这些IPSP是通过脊神经通路被诱发的。电刺激Barrington核可抑制IPSP。结果提示，巴林顿核与节前神经元之间没有直接联系，在排尿期，巴林顿核向节前神经元的下行通路更为便利。这一结果也支持了先前的假说，即巴林顿氏神经元可能参与激活脊髓兴奋通路或抑制阻止节前神经元容易放电的强烈抑制神经机制。此外，还研究了尿路通向外括约肌运动神经元的途径。电刺激盆神经在外括约肌运动神经元上诱发短潜伏期的EPSP和长潜伏期的IPSP：前者是通过脊神经回路诱发的。刺激Barrington核可在括约肌运动神经元诱发IPSP，其潜伏期与盆神经诱发的IPSP相当。背侧灰质连合的神经元被发现在排尿收缩的同时放电。刺激该部位抑制了外括约肌的放电活动。结果支持巴林顿核通过位于灰质背侧连合的抑制性内神经元抑制外括约肌运动神经元的观点。较少

Barrington's nucleus, or pontine micturition center, has been shown to project directly to the sacral preganglionic neurons that innervate the bladder muscle, using neuron tracing technique. We examined whether this nucleus connects directly to sacral preganglionic neurons in anesthetized cats, using electrophysiological technique. Intracellular recordings were made from sacral preganglionic neurons. Single to three electrical shocks applied to Barrington's nucleus evoked no or weak EPSPs in preganglionic neurons when the bladder pressure was low. In fact, stimulation of 30-50 train pulses was needed for Barrington's nucleus to evoke bladder contraction. On the other hand, clear EPSPs were evoked during voiding phase after a single shock to Barrington's nucleus. Latencies of EPSPs were not fixed in any preganglionic neurons, indicating that EPSPs were evoked polysynaptically. Interaction of inputs from Barrington's nucleus and the bladder afferents were further investigated. Electrical … More stimulation of the pelvic afferents evoked IPSPs with short latencies on the sacral preganglionic neurons that innervate the bladder. These IPSPs were evoked via spinal neural pathways. Electrical stimulation of Barrington's nucleus suppressed the IPSPs. The observations suggested that there is no direct connection between Barrington's nucleus and sacral preganglionic neurons, and that the descending pathway from Barrington's nucleus to sacral preganglionic neurons is facilitated during the voiding phase. The results also support the previous hypothesis that Barrington's neurons may participate in either activating the spinal excitatory pathway or disinhibiting a strong inhibitory neural mechanism that prevents preganglionic neurons from discharging easily. The micturition pathway to the external urethral sphincter motoneurons was also investigated. Electrical stimulation of the pelvic nerve evoked EPSPs with short latencies and IPSPs with long latency on the external urethral sphincter motoneurons : the former were evoked via a spinal neural circuit. Stimulation of Barrington's nucleus evoked IPSPs in the sphincter motoneurons, the latency of which was comparable to those IPSPs that were evoked by the pelvic nerve. Neurons in the dorsal gray commissure were found to fire in concert with micturition contraction. Stimulation of this site depressed the firing activity of the external urethral sphincter. The results supported the idea that Barrington's nucleus inhibits the external urethral sphincter motoneuron via inhibitory intemeurons located in the dorsal gray commissure. Less