Structural analysis of dopamine- and amphetamine-induced depolarization currents in the human dopamine transporter.

Amphetamine (AMPH) induces depolarizing currents through the human dopamine transporter (hDAT). Recently we discovered that the S(+) enantiomer of AMPH induces a current through hDAT that persists long after its removal from the external milieu. The persistent current is less prominent for R(-)AMPH and essentially absent for dopamine (DA)-induced currents. Related agents such as methamphetamine also exhibit persistent currents, which are present in both frog oocyte and mammalian HEK expression systems. Here, we study hDAT-expressing Xenopus laevis oocytes voltage-clamped and exposed from outside to DA, S(+)AMPH, R(-)AMPH, and related synthesized compounds, including stereoisomers. The goal of the study was to determine how structural transitioning from dopamine to amphetamine influences hDAT potency and action. At saturating concentrations, S(+)AMPH or R(-)AMPH induce a sharply rising depolarizing current from -60 mV that is comparable in amplitude to DA-induced currents. The magnitude and duration of the currents and the presence or absence of persistent currents depend on the concentration, duration of exposure, and chemical structure and enantiomeric versions of the agents.