Roles of levo-tetrahydropalmatine in modulating methamphetamine reward behavior

Levo-tetrahydropalmatine (L-THP), as an alkaloid purified from the traditional Chinese herbal medicine Corydalis and Stephania, has been widely used to produce many traditional Chinese herbal preparations. The effect of L-THP on methamphetamine-induced reward learning still remains unclear although it has been proved to be effective on treating allodynia and drug addiction. This experiment has been designed to examine the effect of L-THP on the acquisition, expression, extinction, and reinstatement of methamphetamine-induced conditioned place preference (CPP) in mice. The results show that methamphetamine (METH) could induce CPP in mice at doses of 0.5 mg/kg, 1.0 mg/kg and 2.0 mg/kg respectively, but L-THP alone could not do so. Meanwhile, L-THP could not induce conditioned place aversion at doses of 1.25 mg/kg to 20.0 mg/kg in mice, but it could attenuate the acquisition and expression of METH-induced CPP and facilitate the extinction of METH-induced CPP in mice. Besides, L-THP could inhibit the reinstatement of METH-induced CPP at the dose of 10.0 mg/kg whether it was given in the extinction training phase or 30 min before the reinstatement. These results suggest that L-THP can globally suppress the rewarding properties of METH on all phases of the CPP task and it may have potential effects on the treatment of METH abuse. (C) 2013 Elsevier Inc. All rights reserved.