Automated behavioural analysis in animal pain studies

The assessment of the effectiveness of analgesics is strongly based on obse rvational data from behavioural tests. These tests are interesting and give a quantification of the effect of the drugs on the whole animal but their use is subject to several difficulties: (i) many results are difficult to a nalyse as they only correspond to the evaluation of a reflex response; (ii) the tests dealing with more integrated responses are also more difficult t o use and closely depend on the experimenter's subjectivity. If automation is widely used ill a lot of research fields, this is not the case in behavi oural pharmacology. Yet, it can contribute to optimize the tests. The use o f signal processing devices allows the automated land thus objective) measu rement of behavioural reactions to nociceptive stimulation (amplitude of a reflex, vocal emission intensity). Mechanical devices based on a computer-d riven dynamic force detector allows the recording of some pain behaviours. Video image analysis allows the quantification of more complex behaviours ( nociception-induced specific motor behaviours) as well as meaningful inform ation during the same experimentation (exploratory behaviour, total motor a ctivity, feeding behaviour). Moreover, these methods make it possible to ob tain a more objective measurement, to reduce animal-experimenter interactio ns, to ease system use, and to improve effectiveness. The prospects to work in this field are multiple: continuation of the attempts at an automation of the behaviours specifically induced by chronic pain; development of real animal pain monitoring based on analysis of specific and non-specific beha vioural modifications induced by pain. In this context, the automation of t he behavioural analysis is likely to make possible real ethical progress th anks to an increase in the test's effectiveness and a real taking into acco unt of animal's pain. Nevertheless, there are some limits due to characteri stics of the behavioural expression of nociception and technological proble ms. (C) 2001 Academic Press.