Investigation On The Behavior And Related Neuro-Electrochemistry Of Potential Medications For The Treatment Of Substance Use Disorders.

多巴胺（DA）转运体（DAT）是滥用的精神兴奋剂（如可卡因）的主要药理学靶点，也是处方药（如莫达非尼（MOD））的主要靶点，莫达非尼在临床或临床前研究中几乎没有显示出滥用的倾向。最近，我们探索了MOD的神经化学和行为作用，以更好地表征其非典型精神兴奋剂的特征。我们发现MOD在刺激伏隔核壳（NAS）和核心（NAC） DA水平方面的效力和疗效低于可卡因，但在与滥用精神兴奋剂的差异上，伏隔核亚区之间没有统计学上的显著区域差异。在药物鉴别研究中，MOD在较低剂量和较早起效时间下表现出与可卡因类似的主观效应，这是基于其DA效应的预期。这些结果表明，非da依赖性的作用可能在其独特的药理学特征中发挥作用。为了发现MOD作用的潜在非多巴胺能机制，我们将其与哌甲酯的行为和神经化学作用进行了比较。卡贝诺洛酮，一种间隙连接抑制剂，拮抗MOD，但没有哌醋甲酯增强可卡因自我给药。我们的研究结果表明，MOD与可卡因和哌甲酯具有相同的机制，但具有独特的药理学特征，包括促进电紧张偶联和降低滥用倾向，这可能在未来可卡因使用障碍的治疗药物设计中被利用。

The dopamine (DA) transporter (DAT) is the main pharmacologic target of abused psychostimulants like cocaine but also of prescribed medications like modafinil (MOD), which has shown little, if any, propensity for abuse in clinical or preclinical studies. Recently, we have explored the neurochemical and behavioral actions of MOD to better characterize its atypical psychostimulant profile. We found that MOD had a lower potency and efficacy than cocaine in stimulating nucleus accumbens shell (NAS) and core (NAC) DA levels, but, at variance with abused psychostimulants there were no statistically significant regional differences between accumbens subregions. In drug-discrimination studies MOD showed cocaine-like subjective effects at lower doses and earlier onset times than expected based on its DA effects. Those results suggest that non-DA-dependent actions may be playing a role in its unique pharmacological profile. In order to discover a potential non-dopaminergic mechanism for these MOD actions, we compared its behavioral and neurochemical effects with those of methylphenidate. Carbenoxolone, a gap junction inhibitor, antagonized MOD, but not methylphenidate potentiation of cocaine self-administration. Our results indicate that MOD shares mechanisms with cocaine and methylphenidate but has a unique pharmacological profile that includes facilitation of electrotonic coupling and lower abuse liability, which may be exploited in future therapeutic drug design for cocaine use disorder. Though MOD might prove useful as a treatment for specific addicted populations (e.g. heavy crack-cocaine users, or cocaine and methamphetamine addicts without alcohol abuse comorbidity), broader effective medications for psychostimulant use disorders are still an unmet medical need. To this end, several newly synthesized analogs of MOD, for example JJC8-091 and JJC8-088, have been tested in our preclinical models as potential medications for methamphetamine (METH) and cocaine use disorder. JJC8-091 and JJC8-088, were assessed alone and in combination with cocaine to elucidate neurochemical correlates to their divergent behavioral profiles. Despite sharing significant structural similarity, JJC8-088 was more cocaine-like, increasing extracellular DA concentrations in the NAS efficaciously and more potently than JJC8-091. In contrast, JJC8-091 was not self-administered and was effective in blocking cocaine-induced reinstatement to drug seeking. Electrophysiology experiments confirmed that JJC8-091 was more effective than JJC8-088 at inhibiting cocaine-mediated enhancement of DA neurotransmission. Further, when VTA DA neurons in DAT-cre mice were optically stimulated, JJC8-088 produced a significant leftward shift in the stimulation-response curve, similar to cocaine, while JJC8-091 shifted the curve downward, suggesting attenuation of DA-mediated brain reward. Computational models predicted that while JJC8-088 prefers or stabilizes an outward facing conformation of DAT, like cocaine, JJC8-091 stabilizes DAT towards a more occluded conformation. In a recent publication we show that cocaine and cocaine-like typical psychostimulants elicit changes in DA dynamics distinct from those elicited by atypical DAT blockers, as measured via voltammetry procedures. When given in combination, typical DUIs enhance the stimulatory effects of cocaine on evoked DA release while atypical DUIs blunt them. Pretreatments with an inhibitor of CaMKII, a kinase that interacts with DAT and that regulates synapsin phosphorylation and mobilization of reserve pools of DA vesicles, blunted the effects of cocaine on evoked DA release, suggesting a role for CaMKII in modulating the effects of cocaine on evoked DA release without affecting cocaine inhibition of DA reuptake. This effect is related to a specific DAT conformation stabilized by cocaine. Moreover, atypical DUIs, which prefer a distinct DAT conformation, blunt cocaine neurochemical and behavioral effects, indicating a unique mechanism underlying their potential as medications for treating psychostimulant use disorder. We have also extended our studies to investigate the role of sex/gender in the neurochemical effects of typical and atypical DAT blockers. We found that cocaine slowed DA clearance in both male and female mice but produced more robust increases in evoked NAS DA in female mice. R-modafinil produced mild increases in evoked NAS DA and slowed DA clearance across the sexes. The modafinil analog, JJC8-088, a typical DAT inhibitor, produced increases in evoked NAS DA in female and male mice. Finally, JJC8-091, an atypical DAT inhibitor, produced limited increases in evoked NAS DA and slowed DA clearance in both sexes. In this work we begin to tease out how sex differences may alter the effects of DAT targeting and highlight how this may help focus research toward effective treatment options for psychostimulant use disorder. Collectively, these data reveal the underlying molecular mechanism at DAT that may be leveraged to rationally optimize leads for the treatment of psychostimulant use disorder.