Kannan M S, Daniel E E
Am J Physiol. 1980 Jan;238(1):C27-33. doi: 10.1152/ajpcell.1980.238.1.C27.
The structural bases for myogenic and neurogenic control of canine tracheal smooth muscle were studied. At optimum lengths, strips of muscle showed insignificant neurogenic or myogenic tone. Atropine and/or tetrodotoxin blocked the contractile responses elicited on electrical field stimulation of intrinsic nerves. After raising the tone with tetraethylammonium ion and in the presence of atropine, field stimulation of nerves caused a relaxation, a major component of which was blocked by propranolol and/or tetrodotoxin, suggesting an effect mediated through interaction of mediator released from sympathetic nerves with beta-adrenergic receptors. Electron microscopic studies revealed gap junctions between extensions of smooth-muscle cells and a sparse innervation. The axonal varicosities, corresponding to cholinergic (predominantly) and adrenergic (occasionally) nerves, were seen predominantly in the clefts between cell bundles. The physiological responses were compared with the morphological features. Although this muscle exhibits multiunit behavior in vitro, implying that nerves initiate the coordinate activity, its ultrastructural features suggest a potential for single-unit behavior.
对犬气管平滑肌的肌源性和神经源性控制的结构基础进行了研究。在最佳长度时，肌条显示出不明显的神经源性或肌源性张力。阿托品和/或河豚毒素可阻断对内在神经进行电场刺激时引发的收缩反应。在用四乙铵离子提高张力后且在阿托品存在的情况下，对神经进行电场刺激会引起松弛，其中主要成分可被普萘洛尔和/或河豚毒素阻断，这表明一种由交感神经释放的介质与β-肾上腺素能受体相互作用介导的效应。电子显微镜研究揭示了平滑肌细胞突起之间的缝隙连接和稀疏的神经支配。轴突膨体，主要对应胆碱能（主要）和肾上腺素能（偶尔）神经，主要见于细胞束之间的裂隙中。将生理反应与形态学特征进行了比较。尽管该肌肉在体外表现出多单位行为，这意味着神经启动协调活动，但其超微结构特征表明具有单单位行为的潜力。
