IS CHANNEL BLOCKING EFFECT CAUSED BY GENERAL ANESTHETICS PARTICIPATE IN MEMBRANE FLUIDATION?

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There are several possible mechanisms of general anaesthesia including the change of conductance in ionic channels. increased membrane fluidity, and altered responses to neurotransmitters . Ethanol is known to enhance membrane fluidity, and in lipid bilayers. beuzyl alcohol was shown to raise membrane capacitance (C_m). On the other hand, alkyl acetates decreased membrane fluidity in mice. Halothane is an inhaled gemeral anaesthetic, and propofol and thiopental are intravenous general anaesthetics, and all of these three anaesthetics have an inhibitory effect on L-type calcium channel of cardiac. But the effect of these general anaesthetics on C_m is still uncertain. This study was carried out to measure anaesthetic- induced changes in the membrane time constant (tau_m) , which, when coupled with decreased or unchanged input resistance (R_<In>), can be used to deduce changes in C_mThe effects of halothane, propofol and thiopental on membrane capacitance (C_m) in a single guinea-pig veutricular myocyte were examined. Halothane showed slight decrease in Cm. However, propofol and thiopental showed increase in Cm. Because these three anaesthetics all have an inhibitory effect on L-type calcium channel, it is suggested that there would be different mechanisms in the inhibitory effect on ionic channels between halothane and other two intravenous aiiaesthetics other than C_m, alternation.