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The cardiotonic activity of imidazopyridine（MD）

a Chinese-madeproduct of sulmazol（AR-L 115 BS）

was verified and compared withthat of isoprenaline（ISO）on isolated guinea pig atria.The electri-cally-paced left atria were used to determine their positive ino-tropic action

while the spontaneously beating right atria were usedto determine their positive chronotropic action.AS a result

MD showed a strong positive inotropic actioncomparable to that of ISO

and some positive chronotropic actionwhich

however

was much weaker than that of ISO.The positiveinotropic action of a single dose of MD developed quite slowly andincreased gradually in a long time

whereas the action of ISOdeveloped so steeply that its peak effect was reached within a fewminutes.Propranolol could significantly block both inotropic andchronotropic actions of ISO but scarcely those of MD.This suggeststhat MD is not a β

1

-receptor agonist.The experimental resultsdescribed above are similar to those reported abroad.