Elucidating the effects of typical and atypical dopamine uptake inhibitors on the phasic release of dopamine in mice

Abstract

Atypical dopamine uptake inhibitors (DUIs), such as JHW 007, bind to the dopamine transporter (DAT), the same pharmacological target shared by psychostimulants such as cocaine and methamphetamine. Atypical DUIs show lower efficacy compared to typical ones in eliciting motor activation or producing the rewarding/reinforcing effects that might lead to abuse and addiction. These differences may lead to critical discoveries in the development of treatments for psychostimulant use disorders.The goals of this study were to explore the effects of typical (cocaine, methylphenidate, WIN 35 428) and atypical (JHW 007, JJC 8‐091) DUIs on DAT using Fast Scan Cyclic Voltammetry (FSCV) to look at the phasic properties of dopamine release and reuptake, and Fiber Photometry to monitor Ca2+ dynamics during dopamine release in the Nucleus Accumbens of anesthetized male Swiss‐Webster mice. While whole cell patch clamp electrophysiology was used in DAT transfected HEK‐293 cells to examine the dissociation kinetics of DUIs from DAT. Additionally, combinations of DUIs were tested to determine the effects typical and atypical DUIs have on dopamine changes and Ca2+ dynamics produced by cocaine.Results to date indicate that typical and atypical DUIs yield uniquely different effects on the modulation of dopamine release and DAT function. FSCV data shows that DUIs effect the phasic release of dopamine by two mechanisms, increasing the amount of dopamine released per event and decreasing the rate of dopamine reuptake. While a strong correlation can be found between reuptake rate and DAT affinity, the amount of dopamine released per stimulus is dependent on the typicality of the DUI, with higher efficacy for typical compared to atypical DUIs. Similar results were observed for Ca2+ dynamics measured by Fiber Photometry demonstrating that treatment with typical DUIs has a greater impact on Ca2+ fluctuation than treatment with atypical DUIs. Finally, the patch clamp experiments established that the dissociation rate from DAT was correlated to phasic dopamine release and transporter conformation. Finally, tests conducted with combinations of DUIs revealed that the effects of cocaine can be potentiated in combination with typical cocaine‐like DUIs or significantly blunted by pretreatments with atypical DUIs.In summary, our results shed new light on the behavioral and pharmacological differences previously reported between typical and atypical DUIs by elucidating the mechanisms involved at the level of the transporter. Also, results from tests with atypical DUIs administered as pretreatment before cocaine demonstrate the potential of atypical DUIs as pharmacotherapies for psychostimulant use disorders.Support or Funding InformationResearch Funded by: MDP‐NIDA‐IRP, NIH/DHHSThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.