| Methamphetamine (METH) is a highly addictive psychostimulant. METH use and abuse is a growing concern within the United States and throughout the world. In addition, repeated high-dose administrations of METH have been shown to cause persistent striatal dopaminergic deficits in humans, nonhuman primates, and rodents.;Following exocytotic release of DA into the synapse, extracellular DA is transported into the cytosol by the DA transporter (DAT). As such, the DAT is a principal regulator of dopaminergic signaling. Following METH administration, METH disrupts the vesicular sequestration of cytosolic DA through the action of the vesicular monoamine transporter 2 (VMAT2) and causes the reverse-transport of DA through the DAT into the synaptic cleft. While numerous factors have been discovered to contribute to METH toxicity, the underlying mechanisms have not been completely elucidated. It has recently been discovered that multiple, high-dose administrations of METH also cause the formation of higher molecular weight DAT complexes. This dissertation will test the hypothesis that DAT complex formation impairs DAT activity and is associated with METH-induced persistent dopaminergic deficits.;This dissertation demonstrates that METH-induced DAT complex formation negatively correlates with DAT activity and is attenuated by pretreatment with the D2 receptor antagonist, eticlopride, as assessed in striatal synaptosomes 24 h after METH treatment. Intrastriatal injection of 6-hydroxydopamine, a dopaminergic neurotoxin, also causes DAT complex formation. Additionally, DAT complexes do not form in the nucleus accumbens, a brain region that is resistant to METH-induced persistent dopaminergic deficits. DAT complex formation and loss of VMAT2 precede astrocytic activation. Interestingly, DAT complexes increase in molecular weight 48-72 h after treatment, and remain elevated 7 d after treatment. Pretreatment with eticlopride attenuates DAT complex formation, loss of VMAT2, and astrocyte activation as assessed 72 h and 7 d after treatment. This dissertation also presents a novel method to immunoprecipitate DAT which could be used in future studies to identify the composition of the DAT complexes. In conclusion, the work presented in this dissertation demonstrates the association of DAT complex formation with decreased DAT activity and persistent METH-induced dopaminergic deficits. |
