Ohkawa H
Jpn J Physiol. 1978;28(6):833-45. doi: 10.2170/jjphysiol.28.833.
The mechanical activity of the smooth muscle of guinea pig alimentary tract changed during fetal and postnatal development. At the F20 (fetus, body weight 20 g) stage of the fetus, the antrum, small intestinal and colonic preparations showed no spontaneous activity. After this stage, spontaneous activity occurred but the patterns of contractile activity of various regions of the alimentary tract differed from those of the adult. However, at later fetal stages (F50 or later), the mechanical patterns of various regions, except the lower region of colon, were similar to adult patterns. An excitatory response to acetylcholine was observed in all regions at the F20 stage but catecholamines were not effective at this stage. Responses to catecholamines appeared later than those to acetylcholine but they were not constant. During development of the colon, the excitatory effect of adrenaline was significant and the effect was blocked by phenoxybenzamine, and isoprenaline inhibited the spontaneous activity. However, sympathetic nerve stimulation at F70 inhibited the mechanical activity and propranolol blocked the inhibitory action of sympathetic nerves. These results indicate the co-existence of alpha-excitatory and beta-inhibitory receptors on the developing colonic smooth muscle cell membrane.
豚鼠消化道平滑肌的机械活动在胎儿期和出生后发育过程中发生变化。在胎儿的F20（胎儿，体重20克）阶段，胃窦、小肠和结肠标本未显示出自发活动。在此阶段之后，出现自发活动，但消化道各区域的收缩活动模式与成年动物不同。然而，在胎儿后期阶段（F50或更晚），除结肠下部区域外，各区域的机械模式与成年模式相似。在F20阶段，所有区域均观察到对乙酰胆碱的兴奋反应，但在此阶段儿茶酚胺无效。对儿茶酚胺的反应出现晚于对乙酰胆碱的反应，但并不恒定。在结肠发育过程中，肾上腺素的兴奋作用显著，该作用被酚苄明阻断，而异丙肾上腺素抑制自发活动。然而，F70时交感神经刺激抑制机械活动，普萘洛尔阻断交感神经的抑制作用。这些结果表明，发育中的结肠平滑肌细胞膜上存在α兴奋受体和β抑制受体。
