Bornstein J C, Furness J B, Smith T K, Trussell D C
Centre for Neuroscience, Flinders Medical Centre, Bedford Park, South Australia.
J Neurosci. 1991 Feb;11(2):505-18. doi: 10.1523/JNEUROSCI.11-02-00505.1991.
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.
在对豚鼠回肠黏膜进行机械刺激诱发反射的过程中，记录了肠肌间神经丛神经元的活动。对刺入的神经元注入染料（荧光黄或生物胞素），并确定其形态。所有神经元距离刺激部位（使黏膜绒毛变形的刷状刺激）5 - 12毫米。神经元分为S神经元或AH神经元（赫斯特等人，1974年）。刺激部位口侧约40%的S神经元以快速兴奋性突触后电位爆发（平均频率为15 - 40赫兹）做出反应；这些神经元位于上行反射通路中。刺激部位肛侧约60%的S神经元以类似的快速兴奋性突触后电位爆发或缓慢去极化做出反应；这些神经元位于下行通路中。48个AH神经元中只有2个做出反应，且都位于下行通路中。上行或下行通路中的大多数S神经元接收来自至少2个或3个其他神经元的输入。反应过程中诱发的动作电位平均频率为3 - 10赫兹，偶尔会爆发至100赫兹。沿反射通路的传导速度约为0.5米/秒。所有S神经元都是单轴突的，但它们在大小、树突形态和投射方面存在差异。注入生物胞素的S神经元的轴突在肠肌间神经丛内追踪长达7毫米。3个S神经元投射到三级神经丛，可能是纵行肌运动神经元；其中2个位于下行通路中。5个S神经元沿肠道投射，在一些神经节中有曲张侧支。这些神经元可能是中间神经元；3个是下行的，2个是上行的，并且都在相应的反射通路中做出反应。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。其他的在进入环形肌或消失无法检测到之前，沿肠道投射几毫米。通过这项研究，我们能够推断出介导上行和下行黏膜 - 肌肉反射的回路。得出的结论是，AH神经元是初级感觉神经元，而S神经元是回路中的中间神经元和肌肉运动神经元。
