抄録
Although volatile anaesthetics have moderate negative inotropic effects, they potentiate the positive inotropic action of β-adrenoceptor stimulation in isolated myocardium. The objective of the present study was to investigate the effects of sevoflurane (sevo) and halothane (halo) on β-adrenoceptor-mediated increase in L-type Ca2+ current (ICa,L). ICa,L of isolated rabbit ventricular myocytes was measured with whole-cell patch clamp technique. The β-adrenoceptor stimulation was induced by 30 nM isoproterenol (ISO) and similar experiments were performed using 1μM forskolin (adenylate cyclase activator, FSK) to bypass the β-adrenoceptor. Sevo (1.7%) or halo (0.74%) was bubbled in experimental solution and air was bubbled in control group. Sevo and halo decreased ICa,L by 19.8±2.4% and 31.7±3.1%, respectively. In control group, ISO and FSK increased ICa,L to 153±7.0% and 240.3±12.8% ,respectively. While ISO increased ICa,L to 237.2±25.4% and 247.6±16.3% in the presence of sevo and halo, respectively. FSK increased ICa,L to 328.5±36.3% in the presence of sevo, while FSK-induced increase ICa,L was not altered by halo. This study suggests that halo and sevo enhance the effect of β-adrenoceptor stimulation on ICa,L. However the modulations of site are different between halo and sevo. Halo may modulate signal transduction between β-adrenergic stimulation and Ca2+ channel but sevo may enhance the phosphorylation of cAMP-dependent PKA to increase ICa,L. [J Physiol Sci. 2008;58 Suppl:S73]
