Abstract
Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph administration induces transient DAT endocytosis, which, among other Amph effects on dopaminergic neurons, elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT are unknown. Hence, we developed a 14 d Amph-sensitization protocol in knock-in mice expressing HA-epitope-tagged DAT (HA-DAT) and investigated the effects of Amph challenge on sensitized HA-DAT animals. The Amph challenge resulted in the highest locomotor activity on Day 14 in both sexes, which was sustained for 1 h in male but not female mice. Strikingly, significant (by 30-60%) loss of the HA-DAT protein in the striatum was caused by the Amph challenge of sensitized males but not females. Amph also reduced V max of dopamine transport in the striatal synaptosomes of males without changing K m values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT colocalization with the endosomal protein VPS35 only in Amph-challenged males. Amph-induced loss of striatal HA-DAT in sensitized mice was blocked by chloroquine, vacuolin-1, and inhibitor of Rho-associated kinases ROCK1/2, indicative of the involvement of endocytic trafficking in the DAT protein loss. Interestingly, an apparent degradation of HA-DAT protein was observed in the nucleus accumbens and not in the dorsal striatum. We propose that Amph challenge in sensitized mice triggers Rho-mediated endocytosis and post-endocytic trafficking of DAT in a brain-region-specific and sex-dependent manner.