The effect of isoflurane anaesthesia and buprenorphine on the mouse grimace scale and behaviour in CBA and DBA/2 mice

Prevention or alleviation of pain in laboratory mice is a fundamental requirement of in vivo research. The mouse grimace scale (MGS) has the potential to be an effective and rapid means of assessing pain and analgesic efficacy in laboratory mice. Preliminary studies have demonstrated its potential utility for assessing pain in mouse models that involve potentially painful procedures. The next step in validation is to determine if the other procedures that are integral to these models, i.e. anaesthesia or analgesia, result in any changes in MGS score which would need to be taken into account when using this tool to assess post-procedural pain. Here, spontaneous behaviour and MGS data for CBA and DBA/2 mice were recorded at baseline and following either isoflurane anaesthesia (suitable to perform abdominal surgery) or 0.05 mg/kg s.c. buprenorphine. In line with previous studies, isoflurane anaesthesia alone had limited effects on the spontaneous behaviour in either strain of mice. Administration of buprenorphine resulted in increased periods of activity e.g. walking and chewing bedding in CBA mice. These effects were not demonstrated in DBA/2 mice. In comparison, buprenorphine alone had no impact on MGS score in either strain of mice, however DBA/2 mice showed a significant increase in MGS score following isoflurane anaesthesia. The presence of this increased MGS score must be taken into account when attempting to use the MGS to assess pain in DBA/2 mice. Further work should be carried out to establish the presence of this isoflurane effect in other strains and the potential influence of gender on the MGS. This further validation is necessary prior to implementation of this technique in clinical scenarios.