Effect of chloroquine on the motor activity of rabbit stomach were studied with or without combination of ATP-2Na by the balloon technique.
1) Four different doses of chloroquine 1, 3, 5 and 10 mg/kg were injected intravenously. At the doses of 1 and 3mg/kg the drug showed no effect on the gastric motility while at the doses of 5 and 10 mg/kg it showed a marked inhibitory action on the motility and tonus lasting for 4～8 minutes. 2) ATP-2Na was administrated also intravenously in the doses of 3.1 and 6.2 mg/kg. At both doses the drug stimulated the gastric motor activity and tonus after a transient inhibition lasting for an average of 10 minutes. 3) When the motor activity of the stomach was accelerated by ATP-2Na, the addition of chloroquine showed either no effect or proved to be less inhibitory than when the latter was apllied alone. 4) Thus it is clear that chloroquine inhibits the gastric motility in rabbits and that ATP-2Na is antagonistic against chloroquine in this respect.