Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
Life Sci. 2012 Apr 9;90(13-14):495-501. doi: 10.1016/j.lfs.2012.01.004. Epub 2012 Jan 20.
Replacement of smooth muscles by striated muscles occurs in the esophagus during the early postnatal period. The aim of this study was to clarify postnatal changes in vagal control of esophageal muscle contractions in rats.
An isolated segment of the neonatal rat esophagus was placed in an organ bath and the contractile responses were recorded using a force transducer.
Electrical stimulation of the vagus trunk evoked a biphasic contractile response in the neonatal esophageal segment. The first and second components of the contractions were inhibited by α-bungarotoxin and atropine, respectively. Ganglion blockers, hexamethonium and mecamylamine, did not affect vagally mediated contractions. The first component gradually enlarged with age in days, whereas the second component declined during the first week after birth. Application of d-tubocurarine or acetylcholine caused an apparent contraction in the esophageal striated muscle at postnatal day 0, but responses to these drugs were not observed at 1 week after birth. The neonatal esophagus expressed the γ-subunit of nicotinic acetylcholine receptors. In contrast, the ε-subunit was dominantly expressed in the adult esophagus.
The vagus nerves directly innervate both the esophageal striated muscles and smooth muscles in the early neonatal period. During the process of muscle rearrangement, the property of the striated muscles is altered substantially. The specific features of striated muscles in the neonatal rat esophagus might compensate for immature formation of neuromuscular junctions. Unsuccessful conversion of the striated muscle property during postnatal muscle rearrangement would be related to disorders of esophageal motility.
在新生儿期后，食管中的平滑肌被横纹肌取代。本研究旨在阐明大鼠食管肌肉收缩的迷走神经控制的出生后变化。
将新生大鼠食管的一段分离出来，放在器官浴槽中，使用力传感器记录收缩反应。
刺激迷走神经干可诱发新生食管段的双相收缩反应。收缩的第一和第二部分分别被α-银环蛇毒素和阿托品抑制。神经节阻滞剂六烃季铵和美加明不影响迷走神经介导的收缩。第一部分随着日龄的增加而逐渐增大，而第二部分在出生后第一周内下降。在出生后 0 天，给予十烃季铵或乙酰胆碱可引起食管横纹肌明显收缩，但在出生后 1 周后未观察到这些药物的反应。新生大鼠食管表达烟碱型乙酰胆碱受体的γ亚单位。相比之下，ε亚单位在成年食管中占主导地位。
迷走神经在新生儿早期直接支配食管的横纹肌和平滑肌。在肌肉重排过程中，横纹肌的特性发生了很大的改变。新生大鼠食管横纹肌的特定特征可能补偿了未成熟的神经肌肉接头的形成。出生后肌肉重排过程中横纹肌特性的转换不成功可能与食管运动障碍有关。
