Self-injury behaviour induced by intraplantar carrageenan infiltration: a model of tonic nociception.

The research of chronic nociception using whole animals is an approach plagued with methodological drawbacks within the ethical realm, as well as difficulties in the analysis and interpretation of time dependent results. On this work, we propose an experimental model that displays tonic nociception measured as a quantifiable self-injury behaviour (SIB) produced by the inflammation of soft tissue located in the paw of the rat elicited by carrageenan 1% (CAR) infiltration. We established five categories or levels for the analysis of the self-injury behaviour reflecting the intensity of rat nociception triggered by CAR infiltration. In addition, we determine that this model does not induce inescapable pain by noticing no significant differences when measuring weight gain and sexual behaviour. We propose this nociception model as physiologically and ethically appropriate for the study of long-lasting nociception.