Effects of dominant/subordinate social status on pain behavior and proinflammatory cytokines in the serum of mice

The current investigations on Health Equity, primarily point to the harmful health consequences of being in a stressful social hierarchy. The repetitive nature of social conflicts seems to favor the induction of hyperalgesia or hypoalgesia both in rodents and humans, and it can also affect the immune system. In this study, the effects of changes in social status on pain perception as well as alterations of pro-inflammatory cytokines were investigated in Balb/C mice. By implementation of a sensory contact model in 22 male inbred mice (stress group) from 30 mice of the Balb/c strain and modeling of dominance/submissive relationship, each mouse was injected by 20 μl of formalin 2% and their pain behavior was scored, then serum concentrations of proinflammatory cytokines were measured in all mice. Our results showed that subordinate mice in chronic phase of formalin test were hypoalgesic as compared to the control and dominant mice (P<0.05). On the other hand, dominant mice were hypoalgesic as regards to subordinate mice during acute phase of formalin test. IL-1 and IL-6 concentrations in serum of dominant and subordinate mice were well above the control group. These results revealed that despite similar increase of proinflammatory cytokine's level in dominant and subordinate subjects; social status can differently affect pain perception.