The inhibitory effect of levo-tetrahydropalmatine on the methamphetamine-induced spatial memory impairment in mice.

Methamphetamine (METH) administration results in addiction and memory impairment. Previous studies have suggested that levo-tetrahydropalmatine (l-THP), an alkaloid purified from the Chinese herb Corydalis, attenuates the behavioral changes induced by METH. Therefore, in this study, we explored whether l-THP could also protect against the METH-induced memory impairment examined using the Morris water maze (MWM). We found that low dose of METH (1.0 mg/kg) treated for 20 consecutive days prior to the MWM experiment impaired spatial memory retention but not acquisition in mice. In addition, high dose of METH (10.0 mg/kg) treated during the spatial learning phase for five consecutive days impaired both the acquisition and retention of spatial memory. Moreover, both of these impairments induced by METH were reversed by l-THP treatment, indicating a potential protective role of l-THP in METH use.