Uso do exercício resistido antagonizado por naloxone como fator de analgesia em sinovite aguda de joelho de ratos Wistar

analgesia arising from exercising can occur via release of endogenous opioids in the central nervous system and periphery. however, the literature remains controversial about exercise ways and actions in pain. thus, the aim of this study was to evaluate whether resistance exercise produces changes on the nociception and suffers interference by applying an opioid inhibitor. 18 rats divided into three groups were used: g1 - hyperalgesia on right knee and untreated; g2 - hyperalgesia and treated with jumps in water; g3 - hyperalgesia with previous injection of naloxone and subsequent jumps. to produce hyperalgesia,100 ul of 5% formalin was injected in the tibiofemoral joint space. pain was assessed using a digital von frey filament on the right medial tibiofemoral joint. the evaluation periods were: pre-injury (ev1) after 15 minutes (ev2) and 30 minutes (ev3) and one hour (ev4). the applied exercise was jumping in water and it occurred after ev2. the animal performed 4 sets of 5 jumps, with an interval of 3 minutes and overload of 50% of body weight. in g1, nociceptive increase was observed, with significant decrease and return to initial baseline values in av4; g2 showed threshold restoration after exercise and return to baseline; g3 reduced thresholds, without restoration or significant increase in them. we concluded that there was analgesia with use of exercise and that it was altered by blocking beta-endorphin.