1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is known to cause parkinsonism in humans and this fact is a major incentive for using this toxin as an animal model to study the pathogenesis of Parkinson's disease (PD). Although the monkey MPTP model remains the best, most studies have been performed in mice. The so-called acute and sub-acute regimens are commonly used. Both induce tissue striatal dopamine (DA) depletion and nigral neuron death. Tissue striatal DA depletion does not necessarily correlate with impairment of striatal dopaminergic functioning. In freely moving mice, systemic acute or sub-acute MPTP directly induces prolonged release of striatal DA. Such DA release may be considered the first step in MPTP-induced striatal DA depletion. Reportedly, neural stem cells improve symptoms in the MPTP model of PD by interacting with the MPTP-induced pathological nigrostriatal milieu.