Attenuation of methamphetamine induced dopaminergic neurotoxicity by flupirtine: microdialysis study on dopamine release and free radical generation.

Flupirtine is a triaminopyridine derived centrally acting analgetic, which has been found to display neuroprotective effects in models of excitotoxic cell damage, global, and focal ischemia, but no direct interaction with any component of the N-methyl-D-aspartate (NMDA) and glutamate triggered Ca(2+)-channel. Additionally flupirtine shows potent antioxidant effects in isolated mitochondria and cell culture. Work in models of monoamine depletion and neuroleptic induced catalepsy in rats suggests a interaction of flupirtine with the dopaminergic neurotransmitter system as well. This prompted us to examine the effect of flupirtine on methamphetamine toxicity in mice and to investigate the influence on dopamine release and free radical formation in the rat striatum by microdialysis that may explain methamphetamine neurotoxicity. Pretreatment of C57-BL mice with flupirtine (4 x 10 mg/kg) significantly attenuated the striatal dopamine loss after methamphetamine application (4 x 5 mg/kg). In rats, a single injection of 10 mg/kg flupirtine reduced the methamphetamine induced striatal dopamine release by almost 50%, as measured by in vivo microdialysis. Flupirtine, however, did not influence the increase of free radical formation after methamphetamine infusion, which was assayed after infusion of salicylic acid by quantification of 2,3- and 2,5-dihydroxybenzoic acid. This suggests that other mechanisms rather than dopamine metabolism and autoxidation, may contribute to methamphetamine neurotoxicity.