European journal of pain : EJP
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The study of the mechanisms of thermal and mechanical hyperalgesia produced in human inflammatory conditions is dependent on a reliable, consistent model. The present investigation shows that the intraplantar administration of zymosan in the rat hindpaw produces a reliable and quantifiable thermal and mechanical hyperalgesia accompanied by oedema that closely mimics the symptoms of inflammation in man. Prior to the intraplantar injection of zymosan, there was no significant difference in withdrawal latencies, mechanical withdrawal thresholds or paw thickness between the left and right hindpaws. ⋯ In addition, at the greatest dose tested (6.25 mg), all rats showed evidence of licking, biting and shaking of the injected hindpaw for up to 30-45 min after injection. These data demonstrate that the intraplantar injection of zymosan is a reliable and quantifiable model of tonic pain characterized by a dose- and time-dependent thermal and mechanical hyperalgesia accompanied by a robust oedema. This model is likely to be a useful, reliable model in which to study further the central and peripheral mechanisms of hyperalgesia.