ABSTRACT
BACKGROUND: Reactive oxygen species (ROS) is known to be involved in chronic and persistent pain.By using the ROS scavenger 5,5-dimethyl-1-pyrroline N-oxide (DMPO), we studied the effects of ROS on formalin-induced nociception in rats. METHODS: 5% formalin was injected in the left hind paw after intraperitoneal injection of saline or various doses of DMPO (10 mg/kg, 30 mg/kg, 100 mg/kg).Number of flinches was measured in a 5 minute interval for 1 hour. RESULTS: Formalin injected into the left hind paw induced a biphasic nociceptive behaviour. Intraperitoneal injection of DMPO diminished nociceptive behaviors dose-dependently during phase 2 but not phase 1. CONCLUSIONS: ROS might be involved in central sensitization and DMPO, a ROS scavenger, posses antinociceptive property in rats subjected to formalin induced hyperalgesia.