ON THE RAT GASTRIC MOTILITY

Abstract

The origin and the behavior of peristalsis, was studied in correlation with the automaticity of various regions of the stomach, was investigated on the rat stomach in vivo and in vitro. In the stomach in vivi the gastric peristalsis always started every 10 sec. as a ring of contraction which was projected through the root of the left gastric artery at light angle to the curved long axis of the stomach. This area referred to as pacemaker area. The muscle in this area contracted almost synchronously, and this ring of contraction slowly propagated pyloruswards with the velocity of about 1 mm/sec. If the frequency of contractions is used as criterion of automaticity, the fundic strip is in the highest class and the sphincter strip the lowest, and the body and pyloric strips among the middle. 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. When physostigmine was applied, the pacemaker and its adjacent area were enormously increased in tone, but the contractions in their frequency remained almost unchanged and 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. 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.