ETOMIDATE INHIBITS A HUMAN NEURONAL POTAS SIUM CURRENT

Introduction: There is no data available on the action of etomidate on ion currents in human neuronal cells. Therefore the effects of etomid ate on a human neuronal delayed rectifer potassium current were invest igated. Method: Outward rectifying potasium currents of human neurobla stoma SH-SY5Y cells were measured using the whole cell patch-clamp tec hnique. Cells were grown in RPMI-medium (+Pen/Strep and FCS) at 37 deg rees C and 50% CO2. The holding potential was -80 mV. Potassium curren ts were evoked by depolarizing the membrane potential to values from - 50 mV to +90 mV in 10 mV steps using an EPC-7 patch-clamp amplifier (L ist medical electronics) and pclamp Version 5.71 (Axon instruments). R esults: Etomidate differentially inhibited steady-state and peak potas sium current with IC50-values of 170 mu M for peak current suppression and 120 mu M for steady-state current, respectively. Etomidate induce d inactivation-like behaviour of the potassium current and changed the voltage dependence of potassium current activation. Conclusion: The r esults demonstrate that etomidate has more than one effect on the pota ssium current, indicating the complexity of general anaesthetic action s on neuronal targets. The actions of etomidate on human neuronal pota ssium currents may potentially contribute to the myocloni observed wit h this general anaesthetic agent during induction of anaeshtesia.