γ-aminobutyric acid type A receptor β2 subunit mediates the hypothermic effect of etomidate in mice

Abstract

Background: The authors have previously described that the γ-aminobutyric acid type A (GABAA) receptor β2N265S mutation results in a knock-in mouse with reduced sensitivity to etomidate. After recovery from etomidate anesthesia, these mice have improved motor performance and less slow wave sleep. Because most clinically used anesthetics produce hypothermia, the effect of this mutation on core body temperature was investigated. Methods: The effect of etomidate and propofol on core body temperature were measured using radiotelemetry in freely moving GABA A receptor β2N265S mutant mice and wild-type controls. Results: β2N265S mutant mice have a reduced hypothermic response to anesthetic doses of etomidate compared with wild-type controls and after a transient loss of righting reflex regain normothermia more rapidly compared with wild-type controls. Subanesthetic doses of etomidate produce hypothermia, which was not observed in the mutant mice. Vehicle administration resulted in a stress-induced hyperthermic response in both genotypes. Propofol produced a hypothermic response that was similar in both genotypes. Conclusions: The GABAA receptor β2 subunit mediates a significant proportion of the hypothermic effects of etomidate. As the β2 subunit mediates postrecovery ataxia and sedation, anesthetic agents that do not have in vivo potency at β2 subunit-containing receptors offer the potential for surgical anesthesia with improved recovery characteristics.