Impact of inhalation anaesthesia, surgery and analgesic treatment on home cage behaviour in laboratory mice

Anaesthesia and analgesia are used frequently in laboratory routine to ensure animal welfare and good scientific outcomes in experiments that may elicit pain or require immobilisation of the animal. However, there is concern regarding the effect of these procedures on animal behaviour in subsequent experiments. Our study determined the impact of short inhalation anaesthesia (sevoflurane, 15min, 4.9%) and minor surgery (one-sided sham embryo transfer in females, one-sided sham vasectomy in males) with or without pain treatment (carprofen, 5mg/kg, bid) on spontaneous species-specific home cage behaviours in inbred mice. Analysis of 18-h continuous video recordings showed clear post-procedural changes in spontaneous home cage behaviours, with changes of a moderate level after anaesthesia being marked after surgery. Self-grooming, resting and locomotion were the most important behaviours for group separation. Analysis of the temporal distribution of behavioural changes revealed that resting behaviour was altered contradictory to its circadian rhythm as it was decreased in the light phase and increased in the dark phase. Also, locomotion was decreased in the dark phase at 12 to 18h after surgery and anaesthesia. In contrast, self-grooming was increased independently of circadian rhythm, being increased for up to 18h after surgery and anaesthesia. Following surgery, there was no significant difference in duration of behaviours between animals that were treated with carprofen or left without pain relief. In conclusion, it can be assumed that the changes observed in home cage behaviours hint at reduced animal well-being. However, pain or the efficacy of post-operative pain treatment could not be discriminated reliably from the impact of the surgical procedure including inhalation anaesthesia by observing animals’ home cage behaviour. However for the interpretation of behavioural research data, the distinct impact of anaesthesia, surgery, pain treatment and other experimental procedures has to be considered. Our results highlight the requirement for knowledge of species-specific circadian rhythms of behaviours as well as the importance of determining the appropriate time of day for behavioural and welfare assessment.