Addiction Research & Therapy

In experimental animals and humans, exposure to methamphetamine (METH) can produce a loss of dopaminergic (DAergic) nerve terminal markers in the striatum. Furthermore, young adult chronic users of METH are at risk to develop Parkinson’s disease (PD) later in life. Parkin is an ubiquitin-protein ligase with neuroprotective properties that plays an important role in neuroprotection and maintenance of DA neurons. Our laboratory has investigated the role of parkin in protection of DAergic terminals from METH neurotoxicity and in susceptibility of METH-exposed brain to develop PD in young adult rats. We have shown that high-dose METH oxidatively damages parkin and decreases its levels in rat striatum while overexpression of parkin in the nigrostriatal DA system protects DAergic terminals against METH neurotoxicity. We have subsequently investigated molecular mechanisms underlying the parkin-mediated neuroprotection. Loss-of-function mutations in Park2,a gene encoding the E3 ligase parkin, have been found in patients with familial PD and early onset sporadic PD. A deficit in parkin function also contributes to late onset sporadic PD. Despite intense investigation, the exact role of parkin in the development of PD is still unclear as parkin knockout (PKO) rats and mice do not display DAergic defi cits and progressive nigrostriatal DA neuron degeneration. We have set to test the hypothesis that METH-mediated defi cit in parkin combined with other factor(s) decreasing parkin function potentiates the susceptibility of DA to developing PD. We have found that parkin knockout (PKO) rats are hypersensitive to the neurotoxic eff ects of METH in the striatum and display Parkinsonianlike motor impairments. We have also determined that altered DA and phenylethylamine signaling.