Synaptic responses evoked by mechanical stimulation of the mucosa in morphologically characterized myenteric neurons of the guinea-pig ileum
Synaptic responses evoked by mechanical stimulation of the mucosa in morphologically characterized myenteric neurons of the guinea-pig ileum
复制标题
豚鼠回肠形态特征肌间神经元粘膜机械刺激引起的突触反应
作者：
J. Bornstein;J. Furness;T. Smith;D. Trussell
记录从豚鼠回肠肌间神经元的机械刺激粘膜引起的反射过程中。穿刺神经元注射染料（荧光黄或生物胞素），并确定其形状。所有神经元距离刺激物5-12 mm，这是一种使粘膜绒毛变形的刷子行程。神经元被分类为S-神经元或AH-神经元（Hirst等人，1974年）。大约40%的S-神经元对刺激作出快速EPSP（平均频率，15-40 Hz）的爆发反应;这些神经元处于上行反射通路。大约60%的S-神经元对刺激的反应与快速EPSP或缓慢去极化的类似爆发;这些神经元处于下行通路。48个AH-神经元中只有2个有反应，都在下行通路中。大多数S-神经元在上行或下行通路中接受至少2或3个其他神经元的输入。在反应期间诱发的动作电位平均频率为3-10 Hz，偶尔爆发频率高达100 Hz。沿反射通路的传导速度沿着为约0.5米/秒。所有的S-神经元是单轴的，但他们不同的大小，树突形态，和预测。用生物胞素注射的S-神经元的轴突在肌间神经丛内追踪至7 mm。三个S-神经元投射到三级神经丛，可能是纵向肌肉运动神经元;其中2个在下行通路。5个S-神经元沿肠沿着投射，部分神经节内有曲张的侧支。这些神经元可能是中间神经元; 3个下行，2个上行，并且都在适当的反射通路中反应。许多S-神经元有短轴突进入环形肌，可能是环形肌运动神经元。另一些在进入环形肌肉或消失而无法检测之前沿着肠道沿着几毫米。从这项研究中，我们已经能够推导出电路介导的上升和下降粘膜肌肉反射。结论：AH神经元是初级感觉神经元，S神经元是中间神经元和肌肉运动神经元。
Recordings were made from myenteric neurons of the guinea-pig ileum during reflexes evoked by mechanical stimulation of the mucosa. Impaled neurons were injected with dye (Lucifer yellow or biocytin), and their shapes were determined. All neurons were 5–12 mm from the stimulus, a brush stroke that deformed the mucosal villi. Neurons were classified as S-neurons or AH-neurons (Hirst et al., 1974). About 40% of S-neurons oral to a stimulus responded with bursts of fast EPSPs (average frequency, 15–40 Hz); these neurons were in ascending reflex pathways. About 60% of S-neurons anal to a stimulus responded with similar bursts of fast EPSPs or slow depolarizations; these neurons were in descending pathways. Only 2 of 48 AH-neurons responded, both in descending pathways. Most S-neurons in either ascending or descending pathways received inputs from at least 2 or 3 other neurons. Action potentials evoked during a response averaged 3–10 Hz in frequency, with occasional bursts at up to 100 Hz. The speed of conduction along the reflex pathways was about 0.5 m/sec. All S-neurons were uniaxonal, but they differed in size, dendritic morphology, and projections. The axons of S- neurons injected with biocytin were followed up to 7 mm within the myenteric plexus. Three S-neurons projected to the tertiary plexus and were probably longitudinal muscle motor neurons; 2 of these were in descending pathways. Five S-neurons projected along the intestine and had varicose collaterals in some ganglia. These neurons were probably interneurons; 3 were descending and 2 ascending, and all responded in the appropriate reflex pathway. Many S-neurons had short axons that entered the circular muscle and were probably circular muscle motor neurons. Others projected several millimeters along the intestine before entering the circular muscle or fading beyond detection. From this study, we have been able to deduce the circuits mediating ascending and descending mucosa-to-muscle reflexes. It is concluded that AH-neurons are primary sensory neurons and S-neurons are interneurons and muscle motor neurons in the circuits.