Investigação da participação de citocinas inflamatórias na medula espinhal de ratos na dor pós-incisional

Abstract

The several types of pain are generated and maintained by different pathophysiological mechanisms, and should be studied independently. The postoperative pain is a commom and single form of acute pain and despite advances in their study, remains undertreated. Because of persistent pain, even after the use of anti-inflammatory drugs and opiods, we postulated that cytokines may play a key role in post-surgical pain. By means of the data obtained from nociceptive tests, we analyzed the concentration of inflammatory cytokines released by the lumbar segment of spinal cord of rats submitted to the model of postoperative pain. In the von Frey test and Hargreaves test, used to evaluate the mechanical and thermal hyperalgesia, respectively, the animals had a reduction of paw withdrawal thresholds at 1 hour after plantar incision that can be observed until 72 hour after the surgery when compared to animals without incision. Based on these results, the releasing of proinflamatory cytokines IL-1β, IL-6 e TNF-α and anti- inflammatory cytokines IL-10 e IL-4 released by the lumbar spinal cord were analyzed by the chemiluminescence method at 2, 4, 6, 8, 12, 24,48 and 72 hours after the plantar incision. Using the qPCR-RT technique, the gene expression of IL-1β, TNF-α and GFAP were also evaluated at 2, 6, 48 and 72 hours following incision. There was a significant decrease in the release of IL-10 48 hours after the incision when compared to not incised animals. There was no change in the gene expression of IL-1β, however, there was increased in the expression of TNF-α and GFAP 6 hours after the incision when compared to animals not submitted to plantar incision. The plantar incision does not alter the release of cytokines IL-1β, IL-6, TNF-α and IL-4. The maintenance of postoperative pain is not associated with sustained decrease in levels of IL-10. The increase of the expression of TNF-α mRNA is consistent to the increase of the expression of GFAP mRNA and indicates a possible role of astrocytes in the release of cytokines. However, the maintenance of postoperative pain is not associated with constant increase of gene expression of TNF-α. The role of spinal cord release of cytokine in model of postoperative, as well as confirmation of contribution of astrocytes needs investigation.