Relationship between Conformational Changes in the Dopamine Transporter and Cocaine-Like Subjective Effects of Uptake Inhibitors

Cocaine exerts its stimulatory effect by inhibiting the dopamine transporter (DAT). However, novel benztropine- and rimcazole-based inhibitors show reduced stimulant effects compared with cocaine, despite higher affinity and selectivity for DAT. To in-vestigate possible mechanisms, we compared the subjective effects of different inhibitors with their molecular mode of in-teraction at the DAT. We determined how different inhibitors affected accessibility of the sulfhydryl-reactive reagent [2-(tri-methylammonium)ethyl]-methanethiosulfonate to an inserted cysteine (I159C), which is accessible when the extracellular transporter gate is open but inaccessible when it is closed. The data indicated that cocaine analogs bind an open conforma-tion, whereas benztropine and rimcazole analogs bind a closed conformation. Next, we investigated the changes in inhibitio