A rapid oxidation and persistent decrease in the vesicular monoamine transporter 2 after methamphetamine

Methamphetamine (METH) produces long-term decreases in markers of dopamine (DA) terminals in animals and humans. A decrease in the function of the vesicular monoamine transporter 2 (VMAT2) has been associated with damage to striatal DA terminals caused by METH; however, a possible mechanism for this decrease in VMAT2 function has not been defined. The current study showed that METH caused a rapid decrease to 68% of controls in VMAT2 protein immunoreactivity of the vesicular fraction from striatal synaptosomes within 1 h after a repeated high-dose administration regimen of METH. This decrease was associated with a 75% increase in nitrosylation of VMAT2 protein in the synaptosomal fraction as measured by nitrosocysteine immunoreactivity of VMAT2 protein. The rapid decreases in VMAT2 persisted when evaluated 7 days later and were illustrated by decreases in VMAT2 immunoreactivity and DA content of the vesicular fraction to 34% and 51% of control values, respectively. The decreases were blocked or attenuated by prior injections of the neuronal nitric oxide synthase inhibitor, S-methyl-L-thiocitrulline. These studies demonstrate that METH causes a rapid neuronal nitric oxide synthase-dependent oxidation of VMAT2 and long-term decreases in VMAT2 protein and function. The results also suggest that surviving DA terminals after METH exposure may have a compromised capacity to buffer cytosolic DA concentrations and DA-derived oxidative stress.