Effects of volatile anaesthetics on a high conductance calcium dependent potassium channel in cultured hippocampal neurons

(1) The effects of isoflurane and halothane (at nominal concentrations of 4 %) were studied on a high conductance Ca2+ -dependent K+ channel using insi de-out patches from cultured rat hippocampal neurons. (2) With physiologica l-like concentrations of Kf across patches (140 mM internal and 5 mM extern al), unitary activity from a 4 pA channel (conductance near 100 pS) was evi dent in excised patches. (3) Isoflurane or halothane had no effects on unit ary properties of K (Ca) including channel amplitudes and open and closed t imes. The channel open probability was also unchanged in the presence of th e volatile agent. The results suggest that macroscopic high conductance K ( Ca) currents in hippocampal neurons would be relatively insensitive to high concentrations of inhalational anaesthetics. (C) 1998 Elsevier Science Ire land Ltd. All rights reserved.