Introduction: Morphine addiction is a critical health problem. One of the main reasons for morphine abuse and addiction is the rewarding effects of this drug. Echinophora platyloba is an indigenous Iranian plant. This plant has shown analgesic effects that are possibly mediated through opioid receptors. Therefore, the purpose of the present research was to evaluate the possible interference of the hydro-ethanolic extract of this plant on morphine's rewarding effects. Methods: Sixteen groups of mice (n=8) were used in the experiments. Conditioned place preference (CPP) method was used for the evaluation of rewarding effects of morphine (0, 1, 2.5, 5, 10, 15, and 20 mg/kg, s.c.) or the plant extract (0, 12.5, 25, 50, and 100 mg/kg, i.p.) in the mice. Additionally, in the expression experiment, five groups of mice were conditioned with the effective dose of morphine (15 mg/kg). Then, on the test day of the CPP procedure, the plant extract (0, 12.5, 25, 50, and 100 mg/kg, i.p.) was administered one hour before the test. Results: Both morphine and the plant extract could induce a significant conditioned place preference. Moreover, administration of the plant hydroalcoholic extract on the test day could reduce CPP with an effective dose of morphine. Conclusion: Hydroalcoholic extract of Echinophora platyloba may interfere with the rewarding effects of morphine. Therefore, this plant may have therapeutic applications in the treatment or prevention of morphine addiction.
