Mice undergoing neuropathic pain induce anxiogenic-like effects and hypernociception in cagemates.

Rodents can recognize pain-related responses in conspecifics. Therefore, cohabitation with a conspecific animal with chronic pain can potentially promote a stressful situation, which can trigger behavioral changes such as anxiety and depression and alter nociceptive responses. In this study we investigated the effect of cohabitation with a mouse undergoing sciatic nerve constriction (neuropathic pain model). The cagemates were evaluated for nociception (writhing test), anxiety (elevated plus-maze and open field tests), depression (forced swim, tail suspension, and sucrose preference tests), and corticosterone levels. Male Swiss mice were housed in pairs for 14 days, and then divided into three groups: cagemate nerve constriction, in which one animal of each pair was subjected to constriction of the sciatic nerve; cagemate sham, in which one animal from each pair was subjected to the same surgery but without constriction; and control, in which animals were not subjected to any surgical procedure. After 14 days, the cagemates were evaluated using behavioral tests. Social interaction with a conspecific undergoing constriction of the sciatic nerve induced hypernociception and increased anxiety-related responses, whereas in depression tests inconclusive responses and no changes in corticosterone levels were found. In conclusion, cohabitation with suffering conspecifics induces changes in nociceptive responses, as well as in affective responses including anxiety.