Figure 3

Effects of a mineralocorticoid antagonist in a DRG inflammation model. A. Inflammation of the L5 DRG with zymosan/incomplete Freund’s adjuvant (“Zym”) on postoperative day 0 gave a rapid increase in paw withdrawal threshold (PWT) measured with the von Frey method. This was significantly less in animals in which the mineralocorticoid antagonist eplerenone (EPL) was applied locally to the DRG over the same time period, compared to cholesterol (“cho”; chemically inactive control for EPL). * (p < 0.05), ** (p < 0.01), *** (p < 0.001), significant difference between the local EPL and control groups on the indicated day. Systemic EPL, applied subcutaneously (s.c.) did not have the same effect as local EPL. # (p < 0.05), ## (p < 0.01), ### (p < 0.001), significant difference between the local EPL and systemic EPL groups on the indicated day. B. rearing behavior in the same 3 experimental groups plus an unoperated group “Naïve”, measured on day 1. Local EPL reversed the inflammation-induced reduction in rearing observed early after the rats were placed in a novel chamber. C. Excitability of small isolated DRG neurons measured in vitro measured as number of action potentials fired in response to depolarizing currents was significantly increased in neurons isolated from one day after DRG inflammation (middle trace) compared to neurons isolated from normal DRG (top trace); this effect could be reversed by in vitro EPL application (bottom trace). Adapted from reference [53].