Comparative effects of vasectomy surgery and buprenorphine treatment on faecal corticosterone concentrations and behaviour assessed by manual and automated analysis methods in C57 and C3H mice.

Establishing effective cage-side pain assessment methods is essential if post-surgical pain is to be controlled effectively in laboratory animals. Changes to overall activity levels are the most common methods of assessment, but may not be the most appropriate for establishing the analgesic properties of drugs, especially in mice, due their high activity levels. Use of drugs that can affect activity (e.g. opioids) is also a problem. The relative merits of both manual and automated behaviour data collection methods was determined in two inbred mouse strains undergoing vasectomy following treatment with one of 2 buprenorphine dose rates. Body weights and the effects of surgery and buprenorphine on faecal corticosterone were also measured. Surgery caused abnormal behaviour and reduced activity levels, but high dose buprenorphine caused such large-scale increases in activity in controls that we could not establish analgesic effects in surgery groups. Only pain-specific behaviour scoring using the manual approach was effective in showing 0.05 mg/kg buprenorphine alleviated post-vasectomy pain. The C57 mice also responded better to buprenorphine than C3H mice, indicating they were either less painful, or more responsive to its analgesic effects. C3H mice were more susceptible to the confounding effects of buprenorphine irrespective of whether data were collected manually or via the automated approach. Faecal corticosterone levels, although variable, were higher in untreated surgery mice than in control groups, also indicating the presence of pain or distress. Pain-specific scoring was superior to activity monitoring for assessing the analgesic properties of buprenorphine in vasectomised mice. Buprenorphine (0.01 mg/kg), in these strains of male mice, for this procedure, provided inadequate analgesia and although 0.05 mg/kg was more effective, not completely so. The findings support the recommendation that analgesic dose rates should be adjusted in relation to the potential severity of the surgical procedure, the mouse strain, and the individual animals' response.

A comparison of abdominal and scrotal approach methods of vasectomy and the influence of analgesic treatment in laboratory mice.

Vasectomized mice are needed in the production of genetically-modified animals. The BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement recommended that vasectomy should be performed via an incision in the scrotal sac, rather than via laparotomy, arguing that the former could be less painful due to minimal tissue trauma. This study was undertaken to assess the validity of this recommendation. Mice underwent vasectomy via either abdominal or scrotal approach surgery. Mice were filmed for 15 min presurgery and at one, 24 and 48 h postsurgery. Data were obtained using automated behaviour recognition software (HomeCageScan). Meloxicam was administered either alone or combined with acetaminophen prior to surgery. A third group received only saline subcutaneously. Postsurgery behaviour changes were compared between groups at each time point. Exploratory behaviours such as rearing, walking and sniffing were most greatly reduced at one hour following surgery whereas the duration of grooming increased. By 48 h these changes had largely subsided. Results indicated mice undergoing scrotal approach surgery fared better at one hour postsurgery, but the magnitude of this was relatively insignificant compared with the overall effects of surgery. If the observed behaviour changes resulted from pain, results suggested there was no significant advantage of scrotal versus abdominal approach vasectomy. These and other recently obtained data on the effects of non-steroidal anti-inflammatory drugs (NSAIDs) in mice suggest considerably larger doses of these or more potent analgesics, more precise monitoring of surgical outcomes, or a combination of these factors are needed to determine the extent of pain experienced by mice undergoing vasectomy.

Effects of vasectomy surgery and meloxicam treatment on faecal corticosterone levels and behaviour in two strains of laboratory mouse.

Behaviour was assessed in 32 C57BL/6JCrl and 32 C3H/HeN male mice 1 h following vasectomy; saline or meloxicam was administered 30 min prior to surgery at 5, 10, or 20 mg kg(-1). Faeces were collected 24 h prior to, and 3, 6, 9, 12, 24 h following, vasectomy for measurement of faecal corticosterone. Peak corticosterone levels were significantly higher in mice that underwent vasectomy and received saline (p<0.001) or meloxicam at 5 or 10 mg kg(-1) (p=0.021, and p<0.001, respectively) compared with normal un-operated controls. Mice that underwent vasectomy and received 20 mg kg(-1) meloxicam had peak corticosterone levels that were not different from normal un-operated mice (p=0.254). Discriminant analysis was used to identify behaviours responsible for group separation; these were summed to create two behaviour scores. Score 2 (the frequency of flinching, writhing, rear leg lift and press 2) was thought to be pain related; mice that underwent vasectomy and received saline exhibited significantly more of these behaviours than the normal controls (p=0.032), and the mice that received meloxicam (at any dose). Strain differences were observed in both the stress response to vasectomy and the behavioural changes; the C3H/HeN mice had higher pain scores (behaviour Score 2) and peak corticosterone responses than the C57BL/6JCrl mice. We have demonstrated that significant changes occur in the behaviour of mice following vasectomy, and these changes are reduced by use of meloxicam. Vasectomy elicits a rise in corticosterone levels that was only reduced by the highest dose of meloxicam.