A large number of behavioural methods have been developed to investigate nociception and the actions of analgesic drugs in animals. The formalin test is increasingly used as a model of injury-produced pain. The generally accepted method of rating pain used for mice is to count or time paw licks. The aim of this study was to examine scoring properties of other behaviours in the formalin test in mice, and determine the best measure of pain. In the first experiment, the behavioural responses to intraplantar injection of a series of formalin concentrations were assessed. In the second experiment a fixed concentration of formalin was used, and the effects of increasing doses of various analgesic and non-analgesic drugs were examined. A time sampling method with momentary rating of nociceptive behaviours and behavioural state was used. A correlational analysis of the data indicated that combinations of pain behaviours performed better than any single measurement, and the relationship between formalin concentration and behavioural measures were stronger when mice were habituated to the environment prior to testing. All four analgesic agents, morphine, amphetamine, dipyrone and xylazine, produced dose-dependent suppression of pain behaviours. The nociceptive measures were not significantly altered by sedative or neuroleptic drugs. Considering the dose-effect relations for formalin and analgesic and non-analgesic agents, together, indicated that the sum of favouring, lifting and licking was the most consistent measure of both, pain and analgesia.

Abbott, Frances V. (Supervisor)