MORPHINE INCREASES THE BEATING RATE IN CULTURED RAT HEART CELLS / 中国药理学通报

At the concentrations of 10-8mol/L, 5.5?l0-8mol/L, 10-7mol/L morphine produced a dose-dependent increase of beating rate in cultured rat heart cells with 9%,32%and 81% respectively. The increase was antagonized by opiate antagonist naloxone ( 10-5mol/L ) , but not affected by propranolol ( 10-5mol/L ) which could cancel the positive chronotropy of isoprenaline ( 10-9mol/L ) on the beating cells. The results support the concept that morphine may be a direct effect on myocadium, perhaps through opiate receptors.