Ward S M
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno 89557, USA.
Am J Physiol. 1996 Jul;271(1 Pt 1):G184-91. doi: 10.1152/ajpgi.1996.271.1.G184.
The ontogenetic development of the circular muscle layer of the canine proximal colon was studied in animals from midway through gestation to 30 days old. With age, there was an increase in resting membrane potential along the submucosal surface and a decrease along the myenteric surface of the circular layer. Coinciding with the changes in membrane potential, slow waves increased in amplitude along the submucosal border and decreased in amplitude along the myenteric border. Muscle strips from animals midway through gestation were mechanically quiescent; however, 1 wk before birth spontaneous activity was observed. Electrical field stimulation of enteric nerves increased spontaneous contractions; this increase in activity was reversed to inhibition by atropine. In the presence of atropine and N omega-nitro-L-arginine or N omega-nitro-L-arginine methyl ester, a noncholinergic excitation was revealed at stimulation frequencies > 5 Hz. The results of these studies provide evidence that the canine proximal colon is spontaneously rhythmic and that a functional innervation to the circular muscle layer exists before birth. The gradient in resting membrane potential across the circular layer is absent at birth but develops within 2-3 wk after parturition.
研究了从妊娠中期到30日龄犬近端结肠环行肌层的个体发生发育。随着年龄增长，环行肌层黏膜下表面的静息膜电位升高，肌间表面的静息膜电位降低。与膜电位变化一致，慢波在黏膜下边界处振幅增大，在肌间边界处振幅减小。妊娠中期动物的肌条呈机械性静止状态；然而，出生前1周观察到自发活动。肠神经的电场刺激增加了自发收缩；阿托品可将这种活动增加逆转至抑制状态。在存在阿托品和N-ω-硝基-L-精氨酸或N-ω-硝基-L-精氨酸甲酯的情况下，在刺激频率>5Hz时显示出非胆碱能兴奋。这些研究结果证明犬近端结肠具有自发节律性，并且在出生前就存在对环行肌层的功能性神经支配。出生时环行肌层静息膜电位的梯度不存在，但在分娩后2-3周内形成。
