Interaction of volatile anesthetics with β-adrenoceptor stimulations in L-type Ca²⁺ channel current of rabbit ventricular myocytes

Abstract

Volatile anesthetics suppress cardiac contractility. On the other hand, volatile anesthetics, isoflurane, sevoflurane and halothane, were reported to enhance the positive inotropic action of β-adrenoceptor stimulation. In this study, these modulations of volatile anesthetics to β-adrenoceptor stimulation were examined by electrophysiological method. L-type Ca²⁺ channel current (I_Ca,L) of isolated rabbit ventricular myocytes were measured with the whole-cell configuration of patch clamp technique. The β-adrenoceptor stimulation was induced by 30 nM isoproterenol (ISO). Isoflurane (1.15%), sevoflurane (1.7%) or halothane (0.74%) were bubbled in experimental solution and air was bubbled in control group. Isoflurane, sevoflurane and halothane decreased I _Ca,L by 21.3±1.3%, 19.8±2.4%, and 31.7±3.1%, respectively. In control group, ISO increased I _Ca,L to 153.0±7.0%. While ISO increased I _Ca,L to 241.8±14.9%, 237.2±25.4%, and 247.6±16.3% in the presence of isoflurane, sevoflurane, and halothane respectively. These results show that isoflurane, sevoflurane and halothane enhance the effect of β-adrenoceptor stimulation on I _Ca,L. This study suggests that positive inotropic effect of β-adrenoceptor stimulation is enhanced in the presence of volatile anesthetics through increase in I_Ca,L. [J Physiol Sci. 2007;57 Suppl:S229]