Genetic differences affecting the potency of stereoisomers of halothane

The mechanism of action of volatile anesthetics is the subject of some debate. Much of the controversy has centered on whether the site of such actions is purely lipid in nature or may contain a protein target. This report studies the interaction of stereoisomers of halothane on the wild type and on a variety of genetic mutants of Caenorhabditis elegans. The mutants studied have previously been shown to have altered sensitivities to volatile anesthetics. In one mutant, fc34, (R)-halothane [the (+) isomer] was 3 times more potent than its S (-) isomer. Other mutants and wild-type animals displayed more modest differences in sensitivity to the enantiomers. The results indicate that a genetic pathway exists in C. elegans controlling sensitivity to halothane and that both lipid and protein targets may mediate halothane's effects.