Behavioural effects of laparotomy and analgesic effects of ketoprofen and carprofen in rats

Rat behaviour was studied to develop a reliable method of determining the s everity and duration of post-laparotomy pain, and to assess analgesic effec ts of ketoprofen or carprofen. Behaviour was studied in groups of ten anima ls 1 h following subcutaneous (s/c) saline (0.2 ml/100 g), ketoprofen or ca rprofen (5, 10 or 15 mg/kg) given either alone, or prior to surgery. The fr equency of over 150 individual behavioural acts was calculated during the f irst post-treatment hour, the hour immediately prior to darkness, and the f irst 15 min of each of 5 subsequent hours. Discriminant analysis and analys is of variance isolated several easily recognizable behaviours which were m arkedly altered in frequency by surgery. These were unaffected by drug admi nistration alone and were mainly transient, easily quantifiable activities; 'cat-like' back arching, horizontal stretching followed by abdominal writh ing and twitching while inactive. Reductions in the frequency of these beha viours following surgery with analgesic treatment supported the hypothesis that they reflected post-operative pain. Ketoprofen and carprofen were equi potent and no dose related effects were apparent. Analgesic activity lasted between 4 and 5 h with the 5 mg/kg dosage, this being estimated from the d uration of overall and specific behaviour differences between saline and dr ug treated animals. The data provided substantial evidence as to the useful ness of behavioural criteria for estimating pain severity, and for the firs t time, the basis of a system for routine pain assessment and management in rats subjected to abdominal surgery. (C) 2001 International Association fo r the Study of Pain. Published by Elsevier Science B.V. All rights reserved .