Effective alleviation of pain in laboratory animals depends on the ability to recognise pain and assess its severity. Traditional methods of pain assessment based on monitoring of behaviour and clinical signs (e.g. weight loss) are time consuming and can have other limitations (e.g. the signs observed may not be specific to pain).
Research by Dr Jeffrey Mogil and colleagues, McGill University, has demonstrated that changes in facial expression provide a reliable and rapid means of assessing pain in mice, rabbits and rats. ‘Grimace scales’ have been developed for these species, based on changes in a number of ‘facial action units’, such as narrowing of the eyes (orbital tightening) or changes in the position and shape of the whiskers.