Studies on mechanism of retching and vomiting in dogs. Effect of peripheral dopamine blocker on myoelectric changes in antrum and upper small intestine.

In five conscious dogs prepared with a gastric cannula and platinum monopolar electrodes in the antrum, duodenum, and jejunum, the effect of dopamine or copper sulfate on the myoelectric activity was studied. During phase I of interdigestive myoelectric activity, retching, and/or vomiting occurred in 1.6 +/- 0.2 (mean +/- SE) min after intravenous bolus injection of dopamine (50 micrograms/kg) or in 8.7 +/- 1.8 min after intragastric administration of copper sulfate (2%, 50 mg). Immediately prior to the retching and/or vomiting act, a group of disordered myoelectric activities occurred, including retrograde-moving trains of spike activity starting from the jejunum and the subsequent tachyarrhythmia in the antrum. These motility changes also occurred in the two anesthetized dogs so studied. Both the retching and/or vomiting act and the abnormal myoelectric activity which were induced by dopamine and by copper sulfate were prevented by intravenous administration of a peripheral dopamine blocker, domperidone, 5 mg, in 100% and 70%, respectively. Although domperidone could not prevent the retching and/or vomiting induced by copper sulfate in three of 10 experiments, it delayed the onset of vomiting from 8.7 +/- 1.8 to 14.5 +/- 5.3 min. A possible role of peripheral dopamine receptor on the motility disorders associated with retching and/or vomiting has been suggested.