The effects of pressure and pharmacologically active substances on gastric peristalsis in a transmurally stimulated rat soomach-duodenum preparation.

1. A rat stomach-duodenum preparation in which pressures in the body and the antrum and flow through the pylorus could be recorded simultaneously has been used to study the effects of pressure and pharmacologically active substances on the peristalsis induced by transmural stimulation.2. Vagal and transmural stimulation produced vigorous peristalsis and episodic flow. Simultaneous stimulation of the peri-arterial nerves abolished peristalsis and relaxed the pylorus.3. After repeated stimulation the preparation lost tone and peristalsis failed. Peristalsis and tone could then be improved by lowering intragastric pressure. Vigorous peristalsis could be restored in an inactive preparation by eserine and more transiently by 5-HT.4. Drugs which increased smooth muscle tone improved peristalsis and, under the conditions used, they reduced flow. Eserine was more active in this respect than acetylcholine or 5-HT.5. Adrenaline and hyoscine abolished peristalsis and caused the stomach and the pylorus to relax.6. The results suggest that the peristaltic activity of the antrum is more important than the tone of the pylorus itself in controlling gastric emptying.