Introduction: Micronutrients are necessary for human bodies. Reduction or increase in the amount of micronutrients can disrupt normal function of the body. Different micronutrients such as Mg2, Mn2, Zn2 and Cu2 affect the central nervous system and may be effective in pain and inflammation. In this study, the effect of CuCl2 on thermal pain was assessed. Methods: Adult male Wistar rats (200–250 g) were used in this study. Animals were divided into 6 groups (control, sham, CuCl2 (5 mg/kg), CuCl2 (10 mg/kg), CuCl2 (20 mg/kg) and CuCl2 (100 mg/kg)). Animals received CuCl2 peripherally and pain behavior was assessed by tail flick test and data were analysised statistically. Results: All doses of CuCl2 (5, 10, and 20 mg/kg) used in this study elevated the pain threshold and caused thermal analgesia in tail flick test (p<0.0001, p<0.0001, and p<0.007, respectively). Rats that received CuCl2 in 100 mg/kg were died. Conclusion: Previous studies have shown that copper ions are involved in strengthening of analgesic effects of morphine. It is possible that copper induce thermal analgesia by increasing the sensitivity of opioid receptors to endogenous opioids.

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