ENFLURANE IS A POTENT INHIBITOR OF HIGH CONDUCTANCE CA2+-ACTIVATED K+ CHANNELS OF CHARA-AUSTRALIS

The volatile anaesthetic, enflurane, is commonly used in surgery for inducing the state of general anaesthesia. It is assumed, that general anaesthetics act on ion channels, but little is known of how they do so and what kinds of channels are sensitive. We found, that enflurane inhibits a large conductance Ca2+-activated K+ channel of the green alga, Chara australis. Effects occur at clinically relevant concentrations and are fully reversible. The actions of enflurane are distinct from those of charybdotoxin and tetraethylammonium, which are well known blockers of this channel type. Kinetic analysis of single-channel data demonstrates multiple effects of enflurane on the channel protein.