BACKGROUND AND OBJECTIVE: Curcumin is the main ingredient of turmeric which has been used in traditional medicine for pain relief. This study was done to investigate the mechanism of possible analgesic and anti-inflammatory effect of curcumin using hot-plate and formalin method on mice.

METHODS: This experimental study was done on white mice weighing 20-25 g were used. Two approaches including analgesic effects of curcumin at a dose of 10, 20 and 30 mg/kg using Hot-plate method and analgesic with probable anti-inflammatory effects of curcumin at a dose of 5, 10 and 20 mg/kg using formalin test were examined. The data gathered from the experiments was analyzed using statistical methods.

FINDINGS: Curcumin alone on the hot-plate, showed no significant difference in mice latency time compared to saline group. Significant increases in latency time were seen after treatment of curcumin in doses of 10, 20, and 30 mg/kg in combination with morphine (20 mg/kg) at 45 min of hot plate test (22.7±9.8, 25.7±11.2 and 31.1±9.4) and 60 min (22.2±8.8, 25.3±9.7 and 29.1±10.7, respectively) compared to control group (p<0.05). There was a significant difference between curcumin in combination with morphine and saline with morphine (p=0.025 and 0.041, respectively). In formalin test, curcumin alone had a considerable effect in reducing the pain following formalin injection. The formalin test latency at 5 min in curcumin groups (5, 10 and 20 mg/kg) was significant (p<0.05).

CONCLUSION: According to the results, it can be proposed that curcumin acts centrally and its effects on opioid system appear to facilitate the opioids effects. Its effect is dose dependent and can be blocked with naloxone.