Grant: Operating Grant

Parkinson's disease (PD) is a chronic, progressive neurological disorder characterized by resting tremor, bradykinesia, postural instability and rigidity, resulting from the loss of dopamine (DA) neurons in the substantia nigra pars compacta (SNpc). The most vulnerable neurons affected in Parkinson's disease (PD) have the highest density of the phenotypic marker of DA neurons, the plasma membrane dopamine transporter (DAT). DAT is the major controller of DA neuron homeostasis being critically important not only for clearance of released DA from extracellular space but also for maintenance of intracellular DA stores. Thus by altering expression levels of the DAT it is possible to significantly change both extracellular and intracellular DA levels. We recently developed a novel strain of mice over-expressing 6 copies of the DAT gene (DAT-Tg). We propose here to use this strain of mutant mice to evaluate the effect of environmental toxicants known to induce DA cell loss and Parkinosnian phenotypes. There is ample evidence of gene/environment interaction resulting in increased susceptibility of individuals to the deleterious effects of toxicants. Here we propose to directly evaluate whether increases in DAT levels and intracellular DA may increase the toxicity induced by three model toxicants, namely MPTP, rotenone and paraquat. In parallel, we will also directly address whether augmenting DAT levels will lead to increased vulnerability of DA neurons to physiological concentrations of DA and of MPTP. For this, we will use cultured postnatal SN neurons from transgenic mice with varied expression levels of DAT (wild-type (normal expression), DAT-tg (increased expression) and DAT-KO (lack of expression) animals. Using this approach it will be possible to test how DA induced toxicity correlates with DAT levels. This will hopefully allow us to address the specific importance of DAT in DA induced toxicity.