Objective: To study the effect of tetrandrine on morphine induced hyperactivity and reinforcement in mice.Methods: After single administration of morphine and the motion activity was measured by ambulometer

conditioned place-preference paradigm was used to study the reinforcing effect of morphine

climbing behavior was used to evaluate the relation with Dopaminergic system and immediate early expression of c-fos gene in brain was shown by immunohistochemical method.Results: Single administration of morphine could induce hyperactivity

repeated treatment would produce a conditioned place-preference response

tetrandrine 30 or 60 mg/kg hypodermic injection could inhibit the morphine induced hyperactivity

60 mg/kg could inhibit the conditioned place-preference response but no influence on climbing behavior in mice was found. Tetrandrine could inhibit the c-fos gene expression in nucleus accumbens

ventral tegmental and prefrontal cortex in place-preference model formed by morphine.Conclusion: Tetrandrine could inhibit the hyperactivity and conditioned place-preference response induced by morphine

it might relate to reduce the c-fos gene expression in special area of brain in mice.