VOLATILE ANESTHETICS DIRECTLY ACTIVATE BASE-LINE S-K+ CHANNELS IN APLYSIA NEURONS

The actions of halothane on serotonin-sensitive potassium channels (S K+ channels) were studied in sensory neurons of Aplysia. The normalize d open probability of S K+ channels was increased by clinical concentr ations of halothane in cell-attached and excised patches from neurons of the pleural ventrocaudal cluster. No voltage-dependence of channel activation by halothane was observed. Pre-treatment of neurons with 8- bromo-cAMP (8-Br-cAMP) or nordihydroguaiaretic acid (NDGA) had no effe ct on the relative level of channel activation by halothane. S K+ chan nels that were activated by arachidonic acid could also be activated b y halothane and exhibited closely similar amplitude distributions of o pen channel current. Results from these experiments showed that S K+ c hannel activation by halothane did not depend on second messenger modu lation of channel activity. We conclude that it is likely that halotha ne directly activates S K+ channels. (C) 1998 Elsevier Science B.V. Al l rights reserved.