Up-regulation of Proinflammatory Cytokines in Rostral Ventromedial Medulla Contributes to Chronic Postsurgical Pain by Promoting 5-HT Release / 中山大学学报(医学科学版)

ABSTRACT

ObjectiveTo investigate the role of proinflammatory cytokines tumor necrosis factor alpha （TNFα） and interleukin-1β （IL-1β） in rostral ventromedial medulla （RVM） in chronic postsurgical pain （CPSP） induced by skin/muscle incision and retraction （SMIR）. MethodsSD rats were randomly divided into 5 groups： ① Sham group； ② SMIR group； ③ SMIR+TNFα/IL-1β neutralizing antibody group； ④ SMIR+TNFα/IL-1β group and ⑤ SMIR+vehicle group. 50% paw mechanical withdrawal threshold （MWT） was measured by the up-down method， immunofluroscence was used to detect the TNFα and IL-1β expression and ELISA for the 5-Hydroxytryptamine （5-HT） level. ResultsSMIR elicited persistent nociceptive sensitization， upregulated TNFα and IL-1β expression in RVM neurons and astrocytes. Microinjection of TNFα or IL-1β neutralizing antibody into RVM inhibited the development of nociceptive sensitization and decreased the level of 5-HT in both RVM and spinal dorsal horn. While microinjection of recombinant TNFα or IL-1β into RVM enhanced the development of nociceptive sensitization and increased the level of 5-HT in both RVM and spinal dorsal horn. ConclusionUp-regulation of proinflammatory cytokines in RVM may contribute to SMIR induced CPSP by promoting 5-HT release.