Chang et al reported an upregulation of the dopamine transporter in drug naive euthymic bipolar patients, while Anand et al. observed a downregulation in a group consisting of both euthymic bipolar and bipolar depression patients.46, 47 Additionally, one study has assessed the vesicular monoamine transporter protein (VMAT-2), located in presynaptic neurons and involved in the storage of dopamine. This evidence concerns the gene SLC6A3 and bipolar disorder.