Inhibition of Gastric and Cecal Peristalsis in Rabbit by CO 2 + O 2 Inhalations

The effect of carbon dioxide gas upon the motility of the gastro-intestinal canal has been studied chiefly on excised sections of the gut1-4 or by the ingestion of water saturated with CO₂ or by the intragastric injection of the gas itself. 5 As far as we know the effect of CO₂ + O₂ inhalations upon gastric and cecal motility induced by the intragastric injection of air or by the subcutaneous injection of pilocarpine or physostigmine has not been reported. Furthermore, it may be emphasized that the results to be reported were obtained without opening the peritoneal cavity or the use of balloons but simply by inspection of the intact abdomen.

The method is a slight modification of one described sometime ago: 6 preliminary narcotization to reduce or abolish the inhibitory effects of external stimuli; to accomplish this 150 mg sodium barbital per kilo were injected subcutaneously about 30 minutes before the test; after cutting the abdominal hair, which is readily done with a blunt-pointed scissors curved on the flat, both the cecum and most of the stomach including the preantrum may be easily observed through the intact abdominal wall; the antrum itself is not visible, but its contraction is readily indicated by a bulging of the preantrum. If the stomach was not well-filled, 60-120 cc air were injected into this viscus through a hypodermic needle plunged through the abdominal wall. The gas mixtures were 50% each CO₂ and O₂ delivered from tanks at a rate of 150-300 cc per minute each; this gas mixture was administered to the rabbit through a funnel held at such a distance over the nose or the tracheal tube that the respirations were definitely deepened. All observations were 5 minutes long: before, during and after the gas administration.