Curso temporal da liberação local de citocinas inflamatórias no modelo de dor pós incisional em ratos

Abstract

The postoperative pain is a common and single for m of acute pain and despite advances in their study, remains undertreated. Different types of pain are generated and maintained by different pathophysiological mechanisms, therefore the each type of pain should be studied independently. It has been postulated that cytokines may play key role in post-surgical pain. Thus, we analyzed the time course of local release of inflammatory cytokines in the plantar incision model in rats. Initially we analyzed the pattern of thermal and mechanical hyperalgesia using the nociceptive tests of von Frey test and Hargreaves, respectively. Our animals had in both tests lower withdrawal thresholds 1 hour after incision, and this reduction could be observed until 96 hours after surgery as compared with animals without incision. Based on these results, we analyzed the local release of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and anti-inflammatory cytokines IL-10 and IL-4 by chemiluminescence at 2, 6, 8, 24, 48, 72 and 96 hours after the plantar incision. Our results show that plantar incision produced a significant increase in the concentrations of IL-1β and IL-6 six and 8 hours after incision, returning to values not significantly different from controls in the other periods studied. The concentrations of TNF-α were not statistically different from controls at any time study. The concentrations of IL-10 significantly increased 2 hours after incision, returning to values not significantly different from controls in the other periods studied. The levels of IL-4 were higher in the control group, with a significant reduction of the concentration of this cytokine 24 and 48 h after surgery. The maintenance of hyperalgesia does not appear to be associated with a sustained increase in the concentrations of these cytokines at the site of the incision. Different mechanisms and mediators must contribute to the maintenance of the hyperalgesia in this model of postoperative pain.