Protective effects of isoliquiritigenin against methamphetamine-induced neurotoxicity in mice.

Isoliquiritigenin (ISL) suppresses cocaine-induced extracellular dopamine levels and has a neuroprotective effect in cocaine-treated rat brain. Here, we examine the effect of ISL on methamphetamine-induced striatal neurotoxicity. Repeated injections of methamphetamine cause the loss of striatal dopamine transporter (DAT) and tyrosine hydroxylase (TH). Intraperitoneal injection of ISL prior to methamphetamine injection significantly prevented methamphetamine-induced reduction of DAT and TH. ISL also suppressed methamphetamine-induced activation of glial cells. Moreover, ISL impeded the expression of nitric oxide synthase and the activation of NF-kappaB through blockage of its phosphorylation. Our results suggest that ISL protects against methamphetamine-induced neurotoxicity by inhibition of NF-kappaB activation.