Ideally, each animal’s behaviors should be observed and, if an individual is determined to be in pain, then analgesia should be provided. Therefore an analgesic protocol for a group of rodents should be developed and then observation should be used to tailor the individual dosing. This is in contrast to providing an analgesic protocol for an entire group which is a common practice with rodents due to the number of animals utilized per experiment. Assessment of normal as well as pain associated rodent behavior during the day can lead to misinterpretation. To complicate pain recognition further, variation in pain sensitivity and responsiveness to analgesics among different rodent genders and strains has been observed.
Additionally, clinical signs can be interpreted subjectively by different individuals. In order to simplify detection and make it more objective, pain scoring systems can be developed. Individual scoring systems must be developed for specific procedures, species, genders and strains. For example a scoring system for a laparotomy (incision into the abdomen) will not be the same as that needed for a thoracotomy (incision into the thorax). Some analgesics are associated with specific rodent behavioral changes (e.g., walking and grooming is seen under the influence of buprenorphine, while scratching and face washing is seen with ketoprofen and carprofen analgesia). Initial rodent pain studies included red light monitoring of animals during the dark hours of the light cycle with video equipment, and then reviewing the videos. This might be ideal but it is not feasible and practical for most rodent facilities. Recent data shows that it is possible to determine if a rat is in pain by observing it for 5 to 10 minutes postsurgically during the light phase of the light cycle and by utilization of behavioral signs. Therefore, it is recommended that observation of rodents should be performed for a minimum of 5-10 minutes at a time, and personnel observing the animals must be trained in noticing painful animal behavior.
* This is an excerpt from the Veterinary Bioscience