Convergence of reflex pathways excited by distension and mechanical stimulation of the mucosa onto the same myenteric neurons of the guinea pig small intestine
Convergence of reflex pathways excited by distension and mechanical stimulation of the mucosa onto the same myenteric neurons of the guinea pig small intestine
复制标题
粘膜扩张和机械刺激所激发的反射通路会聚到豚鼠小肠的相同肌间神经元上
作者：
T. Smith;J. Bornstein;J. Furness
在体外研究了肠反射通路激活对肌间神经元的形态学和电生理学特征的影响。将豚鼠小肠的开放段的浆膜固定在器官浴中，该器官浴的基部设置有两个气球。从粘膜侧暴露球囊之间5-10 mm宽的肌间神经丛条，并用微电极刺穿神经元。通过使气囊膨胀以扩张肠壁以及通过用刷子使暴露的粘膜绒毛变形来刺激反射通路。穿刺神经元在电生理学上被分类为AH-神经元或S-神经元（Hirst等人，1974），并注射生物胞素以确定它们的形状和突起。58个AH神经元对扩张无反应。相比之下，131个S神经元中有63个对扩张产生快速EPSP;大约三分之一的响应S神经元接受来自上行反射通路的输入，三分之一接受来自下行反射通路的输入，三分之一接受来自上行和下行通路的输入。最后一组中的大多数神经元为三级神经丛提供广泛的静脉曲张分支，可能是纵向肌肉运动神经元。只接受一条通路输入的神经元通常会投射到该通路的方向，其中许多是环形肌肉运动神经元。几乎所有对扩张反应的神经元也通过使绒毛变形而兴奋。当刺激以小于10秒的间隔重复时，由扩张或粘膜变形引起的反应下降。这在上行和下行通路中可见，但在前者中更为突出。即使对反复扩张的反应已经消失，使粘膜变形也能诱发正常反应。它的结论是扩张和变形的粘膜刺激单独的群体的感觉神经元激活反射通路，汇聚到共同的运动神经元，并可能共同的interneurons。
The effects on morphologically and electrophysiologically characterized myenteric neurons of activation of intestinal reflex pathways were examined in vitro. Opened segments of guinea pig small intestine were pinned serosa down in an organ bath that had two balloons set into its base. A 5–10-mm-wide strip of myenteric plexus between the balloons was exposed from the mucosal side, and neurons were impaled with microelectrodes. Reflex pathways were stimulated by inflation of the balloons to distend the intestinal wall, and by deforming the exposed mucosal villi with a brush. Impaled neurons were classified electrophysiologically as AH-neurons or S-neurons (Hirst et al., 1974) and were injected with biocytin to determine their shapes and projections. None of the 58 AH-neurons responded to distension. In contrast, 63 of 131 S-neurons responded to distension with a burst of fast EPSPs; about one-third of the responding S-neurons received input from ascending reflex pathways, one-third received input from descending reflex pathways, and one-third received input from both ascending and descending pathways. Most neurons in this last group supplied extensive varicose branches to the tertiary plexus and were probably longitudinal muscle motor neurons. Neurons receiving input from only one pathway usually projected in the direction of that pathway; many of these were circular muscle motor neurons. Almost all neurons responding to distension were also excited by deforming the villi. Responses evoked by distension or deforming the mucosa declined when stimuli were repeated at intervals less than 10 sec. This was seen in ascending and descending pathways but was more prominent in the former. Deforming the mucosa evoked a normal response even when the response to repeated distensions had disappeared. It is concluded that distension and deforming the mucosa excite separate populations of sensory neurons to activate reflex pathways that converge onto common motor neurons and probably onto common interneurons.