ON THE RAT GASTRIC MOTILITY

Abstract

1. On the rat stomach in vivo and in vitro the origin and the behavior of the peristalsis were studied in correlation with the automaticity of various regions of the stomach.
2. In the stomach in vivo the gastric peristalsis always started every 10 seconds as a ring of contraction which was projected through the root of the left gastric artery at right angle to the curved long axis of the stomach. This area was conveniently referred to as pacemaker area. The muscle contained in this area contracted almost synchronously, and this ring of contraction slowly propagated pyloruswards with the velocity of about 1 mm/sec.
3. If the frequency of contractions is taken as a criterion of automaticity, the fundic strip ranks among the highest class, the sphincter strip among the lowest and the body and pyloric strips among the middle. And it was noted that the strips made from the upper regions always contracted with a regular rhythm, whereas those made from the lower regions contracted with an irregular rhythm.
4. It was found that when physostigmine was applied, the pacemaker and its adjacent area were enormously increased in its tone, but the contractions remained in their frequency almost unchanged and were in their amplitude increased not so significantly, while the pyloric part and sphincter showed only a slight increase in its tone but an enormous rise both in its frequency and amplitude of contractions.
5. The phenomena described above revealed that the pars proventricularis and the body take a role of not only preserving the content but also keeping the rhythmicity constant, while the pyloric part and sphincter take a role of favorably evacuating the content.