l-Scoulerine attenuates behavioural changes induced by methamphetamine in zebrafish and mice

Methamphetamine (METH), a substance with a high potential for abuse and addiction, is a serious worldwide public health problem. METH addicts often show extreme paranoia, anxiety, and depression. Thus, there is no effective medication for the treatment of METH-induced abnormalities. In the present study, we investigated the effects of l-Scoulerine (l-SLR), a tetrahydroprotoberberine (THPBS) alkaloid, on METH-induced anxiety-like behaviour in zebrafish and METH-induced addictive behavior in mice. In the novel tank test, acute administration of METH (2 mg/L) induced a significant decrease in the number of total vertical transitions and time spent in the upper zone. Moreover, METH produced significant avoidance behaviour showing increased swimming time in the central area and high speed movement in the mirror area in the mirror stimulation test; these anxiety-like changes were attenuated by l-SLR. Chronic administration of METH (2 mg/kg) produced a steady increase in locomotor activity and conditioned place preference in mice. l-SLR (5 mg/kg) failed to reduce acute METH-induced hyperlocomotion, but attenuated chronic METH-induced behavioural sensitization and significantly blocked the expression of conditioned place preference induced by METH in mice. The present study suggests that l-SLR may be a promising agent for the treatment of addiction and anxiety induced by METH.