Hyperalgesia following agonistic encounters in DBA/2 intruder mice is not associated with recuperative behaviours

Recent findings concerning the time-course of opioid-mediated social conflict analgesia have revealed the existence of two distinct nociceptive phases. Analgesia lasting between 30-45 minutes postattack is evident in the early phase whilst hyperalgesia is observed in the late phase at around 70-75 min postattack. This pattern of nociception has similarities with that envisaged in the Perceptual-Defensive-Recuperative (PDR) model of fear and pain and is predictive of defense/fear reactions being seen whilst animals are analgesic with recuperative behaviours becoming evident in the hyperalgesic phase. Detailed ethological analysis was conducted on DBA/2 mice exposed to opioid-activating attack parameters in a resident-intruder paradigm and tested in the presence of a nonaggressive conspecific. During the analgesic phase, at 10 min postagonistic encounter, a profile was observed consisting largely of increased measures of static, self-directed, possibly recuperative, behaviours (immobile crouch and autogrooming). In contrast, during the hyperalgesic phase, at 70 minutes postencounter, there was evidence of increased environmental exploration, attending to and avoiding nonaggressive conspecifics but no increases in autogrooming or any other behaviours that could be viewed as being recuperative. It is concluded that under present test conditions, using DBA/2 mice exposed to opioid activating attack parameters, predictions based on the PDR model of fear and pain are not supported.