Volatile anesthetics directly activate baseline 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 normalized open probability of S K+ channels was increased by clinical concentrations 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 effect on the relative level of channel activation by halothane. S K+ channels that were activated by arachidonic acid could also be activated by halothane and exhibited closely similar amplitude distributions of open channel current. Results from these experiments showed that S K+ channel activation by halothane did not depend on second messenger modulation of channel activity. We conclude that it is likely that halothane directly activates S K+ channels.
Winegar
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BD
Department of Anesthesia, room S261, University of California, 513 Parnassus Avenue, San Francisco, CA 94143-0648, USA. bw@eleusis.ucsf.edu
Yost
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CS
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001048:Aplysia; D016718:Arachidonic Acid / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D001481:Basal Metabolism; D006221:Halothane / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D015221:Potassium Channels / Q000187:drug effects*; D015290:Second Messenger Systems / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D014835:Volatilization
D018685:Anesthetics, Inhalation; D015221:Potassium Channels; D001464:Barium; D016718:Arachidonic Acid; D012701:Serotonin; D006221:Halothane