Effects of Trimebutine Maleate on Electrical Activities of Isolated Mammalian Cardiac Preparations

Abstract

Abstract The effects of trimebutine maleate on electrical activity in guinea-pig isolated papillary muscles and rabbit sino-atrial nodes have been studied by means of a standard microelectrode method. In papillary muscles, trimebutine (above 10 μM) decreased the maximum rate of rise (V̇max) and the action potential duration at 90% repolarization (APD90), whereas the resting potential was not significantly altered. As to a decrease in V̇max, trimebutine produced a negative shift of the curve relating V̇max to the resting potential along the voltage axis. Trimebutine also depressed the slow action potentials of papillary muscles produced by 27 mM K and 0·2 mitt Ba. In spontaneously beating sino-atrial node preparations, trimebutine (above 10 μ) decreased the heart rate, V̇max and the rate of diastolic depolarization. These results indicate that trimebutine maleate possesses a depressant action on the electrical activities of the fast- and slow-response fibres of the heart mainly due to inhibitions of both fast Na+ and slow Ca2+ channels.