Differential responses of intracisternal injection of interleukin‐1 β to acute and inflammatory orofacial pain model in freely moving rats

Abstract

AbstractThe present study was performed to investigate the modulatory role of certain interleukin (IL)‐1β in nociception with a nociceptive jaw opening reflex and an orofacial formalin test in freely moving rats. In an acute pain model, 10 pg, 100 pg and 1 ng IL‐1β injected intracisternally did not change the digastric eletromyogram (dEMG). However, 10 ng IL‐1β suppressed dEMG to 76±8 % of control values. In an inflammatory pain model, 10 pg IL‐1β injected intracisternally did not change formalin‐induced noxious behavioral responses. However, 100 pg IL‐1β increased formalin‐induced noxious behavioral responses. At higher dose of 10 ng IL‐1β, it did not increase formalin‐induced behavioral responses. Pretreatment with IL‐1 receptor antagonist abolished hyperalgesic response of 100 pg IL‐1β. These results suggest that the intracisternal injection of IL‐1β modulate the transmission of nociceptive information in the orofacial area. The hypo/hyper‐algesic responses of central cytokines seem to depend on the pain model or dose related manner and the hyperalgesic action seems to be mediated by IL‐1 receptor.