Genetic variability of induction and emergence times for inhalational anaesthetics

Background and objectives: Anaesthetic requirements differ among inbred mouse strains. We tested the genetic influence on induction and arousal times to inhalational anaesthetics in two of these strains. Methods: Five male C57BL/6J (B6) and five male C3H/HeJ (C3) mice were each exposed to five different concentrations of nitrous oxide (N₂O) at five different levels of halothane. Time to sleep and arousal were assessed. Data were analysed by repeated measures of analysis of variance. Results: Halothane, N₂O and genetic strain, all were significant independent factors on the time to sleep, while only N₂O was a significant independent factor on the time to arousal (P = 0.004). B6 mice took significantly longer to fall asleep compared to the C3 mice controlling for halothane and N₂O concentrations (F-ratio = 36, P < 0.0001). The effect of N₂O on time to arousal was only significant for the B6 strain (F-ratio = 10, P = 0.005), and not for the C3 strain (F-ratio = 0.8, P = 0.38). Conclusions: Genetics influences the time to sleep for anaesthetic agents in mice.