Methamphetamine and dopamine neurotoxicity: differential effects of agents interfering with glutamatergic transmission

Abstract

The effects of riluzole and lamotrigine, two agents which interfere with the release of glutamate (GLU), and MK-801, a blocker of N-methyl- d-aspartate (NMDA) receptors, were compared in the model of methamphetamine-induced depletion of dopamine (DA) levels in mice. Repeated injections with methamphetamine (4 × 5 mg/kg i.p.) markedly decreased levels of DA, 3,4-dihydroxy-phenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. When mice were treated with riluzole (2 × 10 mg/kg p.o.), no protection was observed against the decrease in DA and the two metabolites. Lamotrigine (2 × 10 mg/kg p.o.) was also inactive. Treatment with MK-801 (2 × 2.5 mg/kg i.p.) antagonized the decrease in DA, DOPAC and HVA levels induced by the neurotoxin. Thus, unlike an NMDA blocker, drugs that interfere with GLU release did not antagonize the methamphetamine-induced DA neurotoxicity in mice. The consequences of this inactivity are discussed in terms of the reliability of this model to test new drugs with putative efficacy in the treatment of Parkinson's disease.