Effects of surgery and analgesic administration on spontaneous behaviour in singly housed rats

The study examined the use of behaviour in assessing post-laparotomy pain in rats given subcutaneous injections of saline (0.2 ml 100 g(-1)) or the analgesics buprenorphine (0.05 mg kg(-1)) or ketoprofen (5 mg kg(-1)). Procedural control influences (handling/movement, anaesthesia, injections) were studied in a second group. Of 150 behaviours examined, discriminant analysis classified the main treatment effects, and class mean frequencies were compared between treatments within each group. With the exception of buprenorphine treatment, control procedures reduced the frequency of active, attentive and grooming behaviour, and increased sleeping during 24 hours following each treatment. Moving animals to the theatre was the main factor responsible for these changes. Surgery also reduced active and attentive behaviour. Animals given pre-operative saline were more frequently inactive than those given ketoprofen. These effects most likely resulted from post-surgery pain, but this was not significantly diminished with the ketoprofen dose used. In all cases, buprenorphine outweighed these effects, causing a sustained increase in active, inactive and attentive behaviour, such that determination of any analgesic effects was impossible. The study underlined a role for pain assessments based on rat behaviour. Drug-related effects emphasised a need for more comprehensive assessments encompassing procedural influences, before behaviour changes that are potentially pain related may be determined accurately.