Effects of Coptis japonica on morphine-induced conditioned place preference in mice

Morphine, an analgesic with significant abuse potential, is considered addictive because of drug craving and psychological dependence. It is reported that repeated treatment of morphine can produce conditioned place preference (CPP) showing a reinforcing effect in mice. CPP is a useful method for the screening of morphine-induced psychological dependence. In the present study, we investigated the effect of the methanolic extract of Coptis japonica (MCJ) on morphine-induced CPP in mice. Furthermore, we examined c-fos expression in the parietal cortex, piriform cortex, striatum, nucleus accumbens, and hippocampus of the morphine-induced CPP mouse brain. Treatment of MCJ 100 mg/kg inhibited morphine-induced CPP. Expression of c-fos was increased in the cortex, striatum, nucleus accumbens, and hippocampus of the morphine-induced CPP mouse brain. These increases of expression were inhibited by treatment with MCJ 100 mg/kg, compared to the morphine control group. Taken together, these results suggest that MCJ inhibits morphine-induced CPP through the regulation of c-fos expression in the mouse brain.