EFFECTS OF ENFLURANE ON THE VOLTAGE-GATED MEMBRANE CURRENTS OF BOVINE ADRENAL CHROMAFFIN CELLS

The effects of the volatile anesthetic enflurane on voltage-gated ionic currents of bovine adrenal chromaffin cells were studied using the patch clamp technique. Bath application of 3.5% (1.7 mM) enflurane decreased the outward Ca2+-dependent K+ current (I(K(Ca))) 'hump' by 88+/-6% (mean+/-S.E.M., n=5 cells) and the peak inward Ca2+ current by 60+/-3% (n=5), whereas the Ca2+-independent K+ current fell by only 34+/-3% (n=5) and peak inward Na+ current was unchanged. Exposure of excised patch 'BK' Ca2+-dependent K+ channels to 3.5% enflurane revealed that the anesthetic directly suppressed the channel probability of opening by 68+/-10% (n=4) with no effect on open state conductance. The differential sensitivity of depolarizing and hyperpolarizing current pathways may contribute to the biphasic response, excitation and depression, observed in certain neuronal systems in response to this inhalational anesthetic.