Abstract: Objective To determine the influence of parity on the potency of volatile anesthetics in mice.Methods 24 ICR/CD-1 mice(half male and half female) mated one another to compose 12 pairs of parents.Each pair was allowed to produce two succeeding litters.Reproductive characteristics were observed and documented,including litter size at birth,sex ratio at weaning,and neonatal mortality.Body weight was measured at birth,at the time of weaning,and at the time of anesthetic potency determination.At 65～75 days of age,median effective concentration(EC₅₀) of inhaled isoflurane was measured in mice from the two parities by using a bracketing design.Loss of righting reflex was chosen as the successful induction of anesthesia.Results 104 and 109 offspring were obtained in the two parities for the determination of isoflurane EC₅₀.There were no significant differences of reproductive characteristics and body weight across the two parities(P>0.05).Males were heavier than females at weaning and at EC₅₀ determination(P<0.05).No significant differences were found in isoflurane EC₅₀ across the parity,and across the sex within parity.Conclusion Volatile anesthetic potency was identical in mice from two succeeding parities.

Key words: mouse, parity, isoflurane, potency