The effects of sevoflurane on contractile and electrophysiologic properties in isolated guinea pig papillary muscles.

We examined, in guinea pig papillary muscles, whether the negative inotropic effect of sevoflurane is due to the depression of the influx of extracellular Ca2+ or to inhibition of the availability of intracellularly stored Ca2+. Sevoflurane decreased action potential duration and contractile force in a concentration-dependent fashion in normally polarized guinea pig papillary muscles. Sevoflurane produced a depression of contractile force with different rates or patterns of stimulation in the rested state and at low stimulation frequencies. In a potentiated state, sevoflurane did not depress contractile forces. Although sevoflurane decreased action potential duration and contractile force in a concentration-dependent fashion in normal Tyrode's solution, in high K+ Tyrode's solution, it caused a depression of contractile force without a shortening of action potential duration. Sevoflurane also depressed contractile force in normal and high K+ Tyrode's solution with ryanodine 1 microM. Our results suggest that in myocardial contractile force the negative inotropic effect of sevoflurane might be caused by depression of transsarcolemmal Ca2+ influx, accompanied by shortening of the action potential duration.