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Li Y, Wang X, Meng Y, Hu T, Zhao J, Li R, Bai Q, Yuan P, Han J, Hao K, Wei Y, Qiu Y, Li N, Zhao Y. Dopamine reuptake and inhibitory mechanisms in human dopamine transporter. Nature 2024; 632:686-694. [PMID: 39112701 DOI: 10.1038/s41586-024-07796-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 07/05/2024] [Indexed: 08/16/2024]
Abstract
The dopamine transporter has a crucial role in regulation of dopaminergic neurotransmission by uptake of dopamine into neurons and contributes to the abuse potential of psychomotor stimulants1-3. Despite decades of study, the structure, substrate binding, conformational transitions and drug-binding poses of human dopamine transporter remain unknown. Here we report structures of the human dopamine transporter in its apo state, and in complex with the substrate dopamine, the attention deficit hyperactivity disorder drug methylphenidate, and the dopamine-uptake inhibitors GBR12909 and benztropine. The dopamine-bound structure in the occluded state precisely illustrates the binding position of dopamine and associated ions. The structures bound to drugs are captured in outward-facing or inward-facing states, illuminating distinct binding modes and conformational transitions during substrate transport. Unlike the outward-facing state, which is stabilized by cocaine, GBR12909 and benztropine stabilize the dopamine transporter in the inward-facing state, revealing previously unseen drug-binding poses and providing insights into how they counteract the effects of cocaine. This study establishes a framework for understanding the functioning of the human dopamine transporter and developing therapeutic interventions for dopamine transporter-related disorders and cocaine addiction.
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Affiliation(s)
- Yue Li
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xianping Wang
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yufei Meng
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Tuo Hu
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jun Zhao
- Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, China
| | - Renjie Li
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qinru Bai
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Pu Yuan
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Jun Han
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Kun Hao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yiqing Wei
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yunlong Qiu
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Na Li
- Heart Center and Beijing Key Laboratory of Hypertension, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Yan Zhao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
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Pedersen CN, Yang F, Ita S, Xu Y, Akunuri R, Trampari S, Neumann CMT, Desdorf LM, Schiøtt B, Salvino JM, Mortensen OV, Nissen P, Shahsavar A. Cryo-EM structure of the dopamine transporter with a novel atypical non-competitive inhibitor bound to the orthosteric site. J Neurochem 2024. [PMID: 39010681 DOI: 10.1111/jnc.16179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2024] [Revised: 06/28/2024] [Accepted: 07/01/2024] [Indexed: 07/17/2024]
Abstract
The regulation of dopamine (DA) removal from the synaptic cleft is a crucial process in neurotransmission and is facilitated by the sodium- and chloride-coupled dopamine transporter DAT. Psychostimulant drugs, cocaine, and amphetamine, both block the uptake of DA, while amphetamine also triggers the release of DA. As a result, they prolong or even amplify neurotransmitter signaling. Atypical inhibitors of DAT lack cocaine-like rewarding effects and offer a promising strategy for the treatment of drug use disorders. Here, we present the 3.2 Å resolution cryo-electron microscopy structure of the Drosophila melanogaster dopamine transporter (dDAT) in complex with the atypical non-competitive inhibitor AC-4-248. The inhibitor partially binds at the central binding site, extending into the extracellular vestibule, and locks the transporter in an outward open conformation. Our findings propose mechanisms for the non-competitive inhibition of DAT and attenuation of cocaine potency by AC-4-248 and provide a basis for the rational design of more efficacious atypical inhibitors.
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Affiliation(s)
- Clara Nautrup Pedersen
- DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Fuyu Yang
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Samantha Ita
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Yibin Xu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | | | - Sofia Trampari
- DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Caroline Marie Teresa Neumann
- DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | | | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus, Denmark
| | | | - Ole Valente Mortensen
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Poul Nissen
- DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Azadeh Shahsavar
- DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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3
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Lee KH, Won SJ, Oyinloye P, Shi L. Unlocking the Potential of High-Quality Dopamine Transporter Pharmacological Data: Advancing Robust Machine Learning-Based QSAR Modeling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.06.583803. [PMID: 38558976 PMCID: PMC10979915 DOI: 10.1101/2024.03.06.583803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The dopamine transporter (DAT) plays a critical role in the central nervous system and has been implicated in numerous psychiatric disorders. The ligand-based approaches are instrumental to decipher the structure-activity relationship (SAR) of DAT ligands, especially the quantitative SAR (QSAR) modeling. By gathering and analyzing data from literature and databases, we systematically assemble a diverse range of ligands binding to DAT, aiming to discern the general features of DAT ligands and uncover the chemical space for potential novel DAT ligand scaffolds. The aggregation of DAT pharmacological activity data, particularly from databases like ChEMBL, provides a foundation for constructing robust QSAR models. The compilation and meticulous filtering of these data, establishing high-quality training datasets with specific divisions of pharmacological assays and data types, along with the application of QSAR modeling, prove to be a promising strategy for navigating the pertinent chemical space. Through a systematic comparison of DAT QSAR models using training datasets from various ChEMBL releases, we underscore the positive impact of enhanced data set quality and increased data set size on the predictive power of DAT QSAR models.
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Affiliation(s)
- Kuo Hao Lee
- Computational Chemistry and Molecular Biophysics Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse – Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Sung Joon Won
- Computational Chemistry and Molecular Biophysics Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse – Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Precious Oyinloye
- Computational Chemistry and Molecular Biophysics Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse – Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse – Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
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Keighron JD, Bonaventura J, Li Y, Yang JW, DeMarco EM, Hersey M, Cao J, Sandtner W, Michaelides M, Sitte HH, Newman AH, Tanda G. Interactions of calmodulin kinase II with the dopamine transporter facilitate cocaine-induced enhancement of evoked dopamine release. Transl Psychiatry 2023; 13:202. [PMID: 37311803 DOI: 10.1038/s41398-023-02493-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/17/2023] [Accepted: 05/26/2023] [Indexed: 06/15/2023] Open
Abstract
Typical and atypical dopamine uptake inhibitors (DUIs) prefer distinct conformations of the dopamine transporter (DAT) to form ligand-transporter complexes, resulting in markedly different effects on behavior, neurochemistry, and potential for addiction. Here we show that cocaine and cocaine-like typical psychostimulants elicit changes in DA dynamics distinct from those elicited by atypical DUIs, as measured via voltammetry procedures. While both classes of DUIs reduced DA clearance rate, an effect significantly related to their DAT affinity, only typical DUIs elicited a significant stimulation of evoked DA release, an effect unrelated to their DAT affinity, which suggests a mechanism of action other than or in addition to DAT blockade. 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 CaMKIIα, 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. Our results suggest a role for CaMKIIα 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's neurochemical and behavioral effects, indicating a unique mechanism underlying their potential as medications for treating psychostimulant use disorder.
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Affiliation(s)
- Jacqueline D Keighron
- Medication Development Program, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
- Department of Biological and Chemical Science, New York Institute of Technology, Old Westbury, NY, USA
| | - Jordi Bonaventura
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
- Department of Pathology and Experimental Therapeutics, Institut de Neurociències, Universitat de Barcelona, L'Hospitalet de Llobregat, Catalonia, Spain
| | - Yang Li
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jae-Won Yang
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Emily M DeMarco
- Medication Development Program, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Melinda Hersey
- Medication Development Program, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Jianjing Cao
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Walter Sandtner
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Michael Michaelides
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Harald H Sitte
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Amy Hauck Newman
- Medication Development Program, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Gianluigi Tanda
- Medication Development Program, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, USA.
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5
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McKendrick G, Sharma S, Sun D, Randall PA, Graziane NM. Acute and chronic bupropion treatment does not prevent morphine-induced conditioned place preference in mice. Eur J Pharmacol 2020; 889:173638. [PMID: 33039460 DOI: 10.1016/j.ejphar.2020.173638] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/28/2020] [Accepted: 10/07/2020] [Indexed: 12/14/2022]
Abstract
A substantial barrier to the treatment of Opioid Use Disorder (OUD) is the elevated relapse rates in affected patients, and a significant contributor to these events of relapse is exposure to cues and contexts that are intensely associated with prior drug abuse. The neurotransmitter dopamine plays a key role in reward-related behaviors, and previous studies have illustrated that dopamine hypofunction in periods of abstinence serves to prompt drug craving and seeking. We hypothesized that restoration of dopaminergic signaling could attenuate drug-seeking behaviors. Therefore, we investigated whether use of an FDA-approved drug, bupropion, an inhibitor of the dopamine transporter (DAT), or a dopamine uptake inhibitor with high affinity for DAT, JHW 007, was able to decrease preference for a drug-paired context. In these experiments, mice underwent 5 days of non-contingent morphine (10 mg/kg) exposure in a conditioned place preference (CPP) paradigm. We found that systemic injection of bupropion (20 mg/kg, i. p.) or intracranial injection of JHW 007 into the nucleus accumbens shell did not prevent the expression of morphine CPP. We then investigated whether chronic bupropion treatment (via implanted osmotic pumps) would influence morphine CPP. We observed that chronic bupropion treatment for 21 days following morphine conditioning did not attenuate the prolonged preference for morphine-paired contexts. Overall, with our dose and paradigm, neither acute nor chronic bupropion diminishes morphine CPP. Continued studies should address FDA-approved medications and their potential for recovery in OUD patients.
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Affiliation(s)
- Greer McKendrick
- Neuroscience Graduate Program, Penn State College of Medicine, Hershey, PA 17033, USA; Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Sonakshi Sharma
- Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Dongxiao Sun
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Patrick A Randall
- Departments of Anesthesiology and Perioperative Medicine and Pharmacology, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Nicholas M Graziane
- Departments of Anesthesiology and Perioperative Medicine and Pharmacology, Penn State College of Medicine, Hershey, PA 17033, USA.
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Hong WC, Wasko MJ, Wilkinson DS, Hiranita T, Li L, Hayashi S, Snell DB, Madura JD, Surratt CK, Katz JL. Dopamine Transporter Dynamics of N-Substituted Benztropine Analogs with Atypical Behavioral Effects. J Pharmacol Exp Ther 2018; 366:527-540. [PMID: 29945932 DOI: 10.1124/jpet.118.250498] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 06/22/2018] [Indexed: 01/07/2023] Open
Abstract
Atypical dopamine transporter (DAT) inhibitors, despite high DAT affinity, do not produce the psychomotor stimulant and abuse profile of standard DAT inhibitors such as cocaine. Proposed contributing features for those differences include off-target actions, slow onsets of action, and ligand bias regarding DAT conformation. Several 3α-(4',4''-difluoro-diphenylmethoxy)tropanes were examined, including those with the following substitutions: N-(indole-3''-ethyl)- (GA1-69), N-(R)-2''-amino-3''-methyl-n-butyl- (GA2-50), N-2''aminoethyl- (GA2-99), and N-(cyclopropylmethyl)- (JHW013). These compounds were previously reported to have rapid onset of behavioral effects and were presently evaluated pharmacologically alone or in combination with cocaine. DAT conformational mode was assessed by substituted-cysteine accessibility and molecular dynamics (MD) simulations. As determined by substituted-cysteine alkylation, all BZT analogs except GA2-99 showed bias for a cytoplasmic-facing DAT conformation, whereas cocaine stabilized the extracellular-facing conformation. MD simulations suggested that several analog-DAT complexes formed stable R85-D476 "outer gate" bonds that close the DAT to extracellular space. GA2-99 diverged from this pattern, yet had effects similar to those of other atypical DAT inhibitors. Apparent DAT association rates of the BZT analogs in vivo were slower than that for cocaine. None of the compounds was self-administered or stimulated locomotion, and each blocked those effects of cocaine. The present findings provide more detail on ligand-induced DAT conformations and indicate that aspects of DAT conformation other than "open" versus "closed" may facilitate predictions of the actions of DAT inhibitors and may promote rational design of potential treatments for psychomotor-stimulant abuse.
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Affiliation(s)
- Weimin C Hong
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Michael J Wasko
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Derek S Wilkinson
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Takato Hiranita
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Libin Li
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Shuichiro Hayashi
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - David B Snell
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Jeffry D Madura
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Christopher K Surratt
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
| | - Jonathan L Katz
- Department of Pharmaceutical Sciences, Butler University, Indianapolis, Indiana (W.C.H.); Division of Pharmaceutical Sciences (M.J.W., C.K.S.) and Department of Chemistry and Biochemistry (J.D.M.), Duquesne University, Pittsburgh; and Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland (D.S.W., T.H., L.L., S.H., D.B.S., J.L.K.)
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7
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Dassanayake AF, Canales JJ. Replacement treatment during extinction training with the atypical dopamine uptake inhibitor, JHW-007, reduces relapse to methamphetamine seeking. Neurosci Lett 2018; 671:88-92. [PMID: 29452175 DOI: 10.1016/j.neulet.2018.02.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 01/26/2018] [Accepted: 02/12/2018] [Indexed: 12/29/2022]
Abstract
There are currently no approved medications to effectively counteract the effects of methamphetamine (METH), reduce its abuse and prolong abstinence from it. Data accumulated in recent years have shown that a range of N-substituted benztropine (BZT) analogues possesses psychopharmacological features consistent with those of a potential replacement or "substitute" treatment for stimulant addiction. On the other hand, the evidence that antidepressant therapy may effectively prevent relapse to stimulant seeking is controversial. Here, we compared in rats the ability of the BZT analogue and high affinity dopamine (DA) reuptake inhibitor, JHW-007, and the antidepressant, trazodone, administered during extinction sessions after chronic METH self-administration, to alter METH-primed reinstatement of drug seeking. The data showed that trazodone produced paradoxical effects on lever pressing during extinction of METH self-administration, decreasing active, but increasing inactive, lever pressing. JHW-007 did not have any observable effects on extinction training. Importantly, JHW-007 significantly attenuated METH-primed reinstatement, whereas trazodone enhanced it. These findings lend support to the candidacy of selective DA uptake blockers, such as JHW-007, as potential treatments for METH addiction, but not to the use of antidepressant medication as a single therapeutic approach for relapse prevention.
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Affiliation(s)
- Ashlea F Dassanayake
- Division of Psychology, School of Medicine, University of Tasmania, Private Bag 30, Hobart, TAS, 7001, Australia
| | - Juan J Canales
- Division of Psychology, School of Medicine, University of Tasmania, Private Bag 30, Hobart, TAS, 7001, Australia.
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8
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Behavioral economic analysis of the effects of N-substituted benztropine analogs on cocaine self-administration in rats. Psychopharmacology (Berl) 2018; 235:47-58. [PMID: 28932889 DOI: 10.1007/s00213-017-4739-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Accepted: 09/12/2017] [Indexed: 10/18/2022]
Abstract
RATIONALE AND OBJECTIVES Benztropine (BZT) analogs and other atypical dopamine uptake inhibitors selectively decrease cocaine self-administration at doses that do not affect responding maintained by other reinforcers. Those effects were further characterized in the current study using a behavioral economic assessment of how response requirement (price) affects reinforcers obtained (consumption) in rats. METHODS Two groups of rats were trained to press levers with food (45-mg pellet) or cocaine (0.32 mg/kg/injection) reinforcement under fixed-ratio (FR) 5-response schedules. In selected sessions, the FR requirement was increased (5-80) during successive 20-min components to determine demand curves, which plot consumption against price. An exponential function was fitted to the data to derive the consumption at zero price (Q 0) and the rate of decrease in consumption (essential value, EV) with increased price. The BZT analogs, AHN1-055, AHN2-005, JHW007 (3.2-10 or 17.8 mg/kg, each), vehicle, or comparison drugs (methylphenidate, ketamine), were administered i.p. before selected demand-curve determinations. RESULTS Consumption of cocaine or food decreased with increased FR requirement. Each drug shifted the demand curve rightward at the lowest doses and leftward/downward at higher doses. The effects on EV and Q 0 were greater for cocaine than for food-reinforced responding. Additionally, the effects of the BZT analogs on EV and Q 0 were greater than those obtained with a standard dopamine transport inhibitor, methylphenidate, and the NMDA antagonist, ketamine (1.0-10.0 mg/kg, each). With these latter drugs, the demand-curve parameters were affected similarly with cocaine and food-maintained responding. CONCLUSIONS The current findings, obtained using a behavioral economic assessment, suggest that BZT analogs selectively decrease the reinforcing effectiveness of cocaine.
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Avelar AJ, Cao J, Newman AH, Beckstead MJ. Atypical dopamine transporter inhibitors R-modafinil and JHW 007 differentially affect D2 autoreceptor neurotransmission and the firing rate of midbrain dopamine neurons. Neuropharmacology 2017; 123:410-419. [PMID: 28625719 PMCID: PMC5546153 DOI: 10.1016/j.neuropharm.2017.06.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/17/2017] [Accepted: 06/14/2017] [Indexed: 12/12/2022]
Abstract
Abuse of psychostimulants like cocaine that inhibit dopamine (DA) reuptake through the dopamine transporter (DAT) represents a major public health issue, however FDA-approved pharmacotherapies have yet to be developed. Recently a class of ligands termed "atypical DAT inhibitors" has gained attention due to their range of effectiveness in increasing extracellular DA levels without demonstrating significant abuse liability. These compounds not only hold promise as therapeutic agents to treat stimulant use disorders but also as experimental tools to improve our understanding of DAT function. Here we used patch clamp electrophysiology in mouse brain slices to explore the effects of two atypical DAT inhibitors (R-modafinil and JHW 007) on the physiology of single DA neurons in the substantia nigra and ventral tegmental area. Despite their commonalities of being DAT inhibitors that lack cocaine-like behavioral profiles, these compounds exhibited surprisingly divergent cellular effects. Similar to cocaine, R-modafinil slowed DA neuron firing in a D2 receptor-dependent manner and rapidly enhanced the amplitude and duration of D2 receptor-mediated currents in the midbrain. In contrast, JHW 007 exhibited little effect on firing, slow DAT blockade, and an unexpected inhibition of D2 receptor-mediated currents that may be due to direct D2 receptor antagonism. Furthermore, pretreatment with JHW 007 blunted the cellular effects of cocaine, suggesting that it may be valuable to investigate similar DAT inhibitors as potential therapeutic agents. Further exploration of these and other atypical DAT inhibitors may reveal important cellular effects of compounds that will have potential as pharmacotherapies for treating cocaine use disorders.
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Affiliation(s)
- Alicia J Avelar
- Department of Cellular and Integrative Physiology, UT Health Science Center, San Antonio, TX, 78229, USA.
| | - Jianjing Cao
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA.
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA.
| | - Michael J Beckstead
- Department of Cellular and Integrative Physiology, UT Health Science Center, San Antonio, TX, 78229, USA.
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Hiranita T, Hong WC, Kopajtic T, Katz JL. σ Receptor Effects of N-Substituted Benztropine Analogs: Implications for Antagonism of Cocaine Self-Administration. J Pharmacol Exp Ther 2017; 362:2-13. [PMID: 28442581 PMCID: PMC5454590 DOI: 10.1124/jpet.117.241109] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/20/2017] [Indexed: 11/22/2022] Open
Abstract
Several N-substituted benztropine (BZT) analogs are atypical dopamine transport inhibitors as they have affinity for the dopamine transporter (DAT) but have minimal cocaine-like pharmacologic effects and can block numerous effects of cocaine, including its self-administration. Among these compounds, N-methyl (AHN1-055), N-allyl (AHN2-005), and N-butyl (JHW007) analogs of 3α-[bis(4'-fluorophenyl)methoxy]-tropane were more potent in antagonizing self-administration of cocaine and d-methamphetamine than in decreasing food-maintained responding. The antagonism of cocaine self-administration (0.03-1.0 mg/kg per injection) with the above BZT analogs was reproduced in the present study. Further, the stimulant-antagonist effects resembled previously reported effects of pretreatments with combinations of standard DAT inhibitors and σ1-receptor (σ1R) antagonists. Therefore, the present study examined binding of the BZT analogs to σRs, as well as their in vivo σR antagonist effects. Each of the BZT analogs displaced radiolabeled σR ligands with nanomolar affinity. Further, self-administration of the σR agonist DTG (0.1-3.2 mg/kg/injection) was dose dependently blocked by AHN2-005 and JHW007 but potentiated by AHN1-055. In contrast, none of the BZT analogs that were active against DTG self-administration was active against the self-administration of agonists at dopamine D1-like [R(+)-SKF 81297, (±)-SKF 82958 (0.00032-0.01 mg/kg per injection each)], D2-like [R(-)-NPA (0.0001-0.0032 mg/kg per injection), (-)-quinpirole (0.0032-0.1 mg/kg per injection)], or μ-opioid (remifentanil, 0.0001-0.0032 mg/kg per injection) receptors. The present results indicate that behavioral antagonist effects of the N-substituted BZT analogs are specific for abused drugs acting at the DAT and further suggest that σR antagonism contributes to those actions.
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Affiliation(s)
- Takato Hiranita
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Weimin C Hong
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Theresa Kopajtic
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
| | - Jonathan L Katz
- Psychobiology Section, Molecular Neuropsychiatry Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health (T.H., T.K., J.L.K.), and Department of Pharmaceutical Sciences, Butler University (W.C.H.), Indianapolis, Indiana
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11
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Relapse to cocaine seeking in an invertebrate. Pharmacol Biochem Behav 2017; 157:41-46. [PMID: 28455125 DOI: 10.1016/j.pbb.2017.04.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 04/07/2017] [Accepted: 04/21/2017] [Indexed: 12/21/2022]
Abstract
Addiction is characterised by cycles of compulsive drug taking, periods of abstinence and episodes of relapse. The extinction/reinstatement paradigm has been extensively used in rodents to model human relapse and explore underlying mechanisms and therapeutics. However, relapse to drug seeking behaviour has not been previously demonstrated in invertebrates. Here, we used a cocaine conditioned place preference (CPP) paradigm in the flatworm, planarian, followed by extinction and reinstatement of drug seeking. Once baseline preference was established for one of two distinctly textured environments (i.e. compartments with a coarse or smooth surface), planarian received pairings of cocaine (5μM) in the non-preferred, and vehicle in the most preferred, environment, and were tested for conditioning thereafter. Cocaine produced robust CPP, measured as a significant increase in the time spent in the cocaine-paired compartment. Subsequently, planarian underwent extinction training, reverting back to their original preference within three sessions. Brief exposure to cocaine (5μM) or methamphetamine (5μM) reinstated cocaine-seeking behaviour. By contrast, the high affinity dopamine transporter inhibitor, (N-(n-butyl)-3α-[bis (4-fluorophenyl) methoxy]-tropane) (JHW007), which in rodents exhibits a neurochemical and behavioural profile distinct from cocaine, was ineffective. The present findings demonstrate for the first time reinstatement of extinguished cocaine seeking in an invertebrate model and suggest that the long-term adaptations underlying drug conditioning and relapse are highly conserved through evolution.
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Grimm SH, Höfner G, Wanner KT. MS Binding Assays for the Three Monoamine Transporters Using the Triple Reuptake Inhibitor (1R,3S)-Indatraline as Native Marker. ChemMedChem 2015; 10:1027-39. [PMID: 25899387 DOI: 10.1002/cmdc.201500084] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Indexed: 11/05/2022]
Abstract
We herein present label-free, mass-spectrometry-based binding assays (MS Binding Assays) for the human dopamine, norepinephrine, and serotonin transporters (hDAT, hNET, and hSERT). Using this approach both enantiomers of the triple reuptake inhibitor indatraline as well as its cis-configured diastereomer were investigated toward hDAT, hNET, and hSERT in saturation experiments. The dissociation rate constants for (1R,3S)-indatraline binding at hDAT, hNET, and hSERT were determined in kinetic studies. These experiments revealed an allosteric effect of clomipramine on the dissociation of (1R,3S)-indatraline from hSERT. Finally, a comprehensive set of known monoamine transport inhibitors and substrates was studied in competition experiments at hDAT, hNET, and hSERT, using (1R,3S)-indatraline as nonlabeled marker. The results are in excellent agreement with those reported for radioligand binding assays. Therefore, the established MS Binding Assays are a promising alternative to the latter for the characterization of new monoamine reuptake inhibitors at DAT, NET, and SERT.
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Affiliation(s)
- Stefanie H Grimm
- Department Pharmazie-Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstr. 7, 81377 Munich (Germany)
| | - Georg Höfner
- Department Pharmazie-Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstr. 7, 81377 Munich (Germany)
| | - Klaus T Wanner
- Department Pharmazie-Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstr. 7, 81377 Munich (Germany).
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13
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Thermal Stability of Dopamine Transporters. J Membr Biol 2015; 248:775-81. [DOI: 10.1007/s00232-015-9794-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 03/16/2015] [Indexed: 11/25/2022]
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Reith ME, Blough BE, Hong WC, Jones KT, Schmitt KC, Baumann MH, Partilla JS, Rothman RB, Katz JL. Behavioral, biological, and chemical perspectives on atypical agents targeting the dopamine transporter. Drug Alcohol Depend 2015; 147:1-19. [PMID: 25548026 PMCID: PMC4297708 DOI: 10.1016/j.drugalcdep.2014.12.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/04/2014] [Accepted: 12/04/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND Treatment of stimulant-use disorders remains a formidable challenge, and the dopamine transporter (DAT) remains a potential target for antagonist or agonist-like substitution therapies. METHODS This review focuses on DAT ligands, such as benztropine, GBR 12909, modafinil, and DAT substrates derived from phenethylamine or cathinone that have atypical DAT-inhibitor effects, either in vitro or in vivo. The compounds are described from a molecular mechanistic, behavioral, and medicinal-chemical perspective. RESULTS Possible mechanisms for atypicality at the molecular level can be deduced from the conformational cycle for substrate translocation. For each conformation, a crystal structure of a bacterial homolog is available, with a possible role of cholesterol, which is also present in the crystal of Drosophila DAT. Although there is a direct relationship between behavioral potencies of most DAT inhibitors and their DAT affinities, a number of compounds bind to the DAT and inhibit dopamine uptake but do not share cocaine-like effects. Such atypical behavior, depending on the compound, may be related to slow DAT association, combined sigma-receptor actions, or bias for cytosol-facing DAT. Some structures are sterically small enough to serve as DAT substrates but large enough to also inhibit transport. Such compounds may display partial DA releasing effects, and may be combined with release or uptake inhibition at other monoamine transporters. CONCLUSIONS Mechanisms of atypical DAT inhibitors may serve as targets for the development of treatments for stimulant abuse. These mechanisms are novel and their further exploration may produce compounds with unique therapeutic potential as treatments for stimulant abuse.
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Affiliation(s)
- Maarten E.A. Reith
- Department of Psychiatry, New York University School of Medicine, New York, NY 10016, USA,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA,Corresponding author: Maarten E.A. Reith, Department of Psychiatry, Alexandria Center of Life Sciences, New York University School of Medicine, 450 E 29th Street, Room 803, New York, NY 10016. Tel.: 212 - 263 8267; Fax: 212 – 263 8183;
| | - Bruce E. Blough
- Center for Drug Discovery, Research Triangle Institute, Research Triangle Park, NC 27709, USA
| | - Weimin C. Hong
- Psychobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Kymry T. Jones
- Department of Psychiatry, New York University School of Medicine, New York, NY 10016, USA
| | - Kyle C. Schmitt
- Department of Psychiatry, New York University School of Medicine, New York, NY 10016, USA
| | - Michael H. Baumann
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - John S. Partilla
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Richard B. Rothman
- Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
| | - Jonathan L. Katz
- Psychobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA
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Hiranita T. Cocaine Antagonists; Studies on Cocaine Self-Administration. JOURNAL OF ALCOHOLISM AND DRUG DEPENDENCE 2015; 3. [PMID: 27398394 DOI: 10.4172/2329-6488.1000e125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Takato Hiranita
- Division of Neurotoxicology, National Center for Toxicological Research (NCTR), U.S. Food and Drug Administration (FDA), USA
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Kohut SJ, Hiranita T, Hong SK, Ebbs AL, Tronci V, Green J, Garcés-Ramírez L, Chun LE, Mereu M, Newman AH, Katz JL, Tanda G. Preference for distinct functional conformations of the dopamine transporter alters the relationship between subjective effects of cocaine and stimulation of mesolimbic dopamine. Biol Psychiatry 2014; 76:802-9. [PMID: 24853388 PMCID: PMC4353924 DOI: 10.1016/j.biopsych.2014.03.031] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 03/08/2014] [Accepted: 03/13/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND Subjective effects of cocaine are mediated primarily by dopamine (DA) transporter (DAT) blockade. The present study assessed the hypothesis that different DAT conformational equilibria regulate differences in cocaine-like subjective effects and extracellular DA induced by diverse DA-uptake inhibitors (DUIs). METHODS The relationship between cocaine-like subjective effects and stimulation of mesolimbic DA levels by standard DUIs (cocaine, methylphenidate, WIN35,428) and atypical DUIs (benztropine analogs: AHN1-055, AHN2-005, JHW007) was investigated using cocaine discrimination and DA microdialysis procedures in rats. RESULTS All drugs stimulated DA levels with different maxima and time courses. Standard DUIs, which preferentially bind outward-facing DAT conformations, fully substituted for cocaine, consistently producing cocaine-like subjective effects at DA levels of 100-125% over basal values, regardless of dose or pretreatment time. The atypical DUIs, with DAT binding minimally affected by DAT conformation, produced inconsistent cocaine-like subjective effects. Full effects were obtained, if at all, only at a few doses and pretreatment times and at DA levels 600-700% greater than basal values. Importantly, the linear, time-independent, relationship between cocaine-like subjective effects and DA stimulation obtained with standard DUIs was not obtained with the atypical DUIs. CONCLUSIONS These results suggest a time-related desensitization process underlying the reduced cocaine subjective effects of atypical DUIs that may be differentially induced by the binding modalities identified using molecular approaches. Since the DAT is the target of several drugs for treating neuropsychiatric disorders, such as attention-deficit/hyperactivity disorder, these results help to identify safe and effective medications with minimal cocaine-like subjective effects that contribute to abuse liability.
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Affiliation(s)
- Stephen J Kohut
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Takato Hiranita
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Soo-Kyung Hong
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland; Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Aaron L Ebbs
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Valeria Tronci
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Jennifer Green
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Linda Garcés-Ramírez
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland; Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, México
| | - Lauren E Chun
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Maddalena Mereu
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Amy H Newman
- Medicinal Chemistry Sections, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland; Medications Development Program, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Jonathan L Katz
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland
| | - Gianluigi Tanda
- Psychobiology, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland; Medications Development Program, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse/Intramural Research Program/National Institutes of Health/Department of Health and Human Services, Baltimore, Maryland.
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Ferragud A, Velázquez-Sánchez C, Canales JJ. Modulation of methamphetamine's locomotor stimulation and self-administration by JHW 007, an atypical dopamine reuptake blocker. Eur J Pharmacol 2014; 731:73-9. [PMID: 24675149 DOI: 10.1016/j.ejphar.2014.03.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 02/20/2014] [Accepted: 03/17/2014] [Indexed: 11/28/2022]
Abstract
JHW 007 [N-(n-butil)-3α-[bis(4'-fluorophenil)methoxi]-tropane] belongs to the family of N-substituted benztropine (BZT) analogs, atypical dopamine transporter (DAT) blockers that are able to strongly modulate cocaine- and amphetamine-related behavior. In the present study, we tested in rats the ability of JHW 007 to alter the stimulant and reinforcing properties of methamphetamine (METH) using locomotor activity, fixed ratio and progressive ratio (PR) self-administration tests. The results showed that JHW 007 attenuated METH-induced locomotor stimulation in a dose-dependent manner and had no stimulant effects when administered alone. The BZT analog, given as a pre-treatment, attenuated METH self-administration without affecting responding for sucrose. In the PR tests JHW 007 produced an increase of the breaking point achieved for both METH- and sucrose self-administration, suggesting that the ability of the BZT analog to reduce self-administration may be linked to its ability to enhance the reinforcing properties of METH. Taken together, these data suggest that DAT inhibition with a high affinity blocker such as JHW 007 can exert differential effects on METH-associated behaviors, reducing METH-induced motor stimulation but augmenting METH׳s reinforcing effects.
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Affiliation(s)
- A Ferragud
- Department of Psychology, University of Canterbury, Christchurch, New Zealand
| | - C Velázquez-Sánchez
- Department of Psychology, University of Canterbury, Christchurch, New Zealand
| | - J J Canales
- Department of Psychology, University of Canterbury, Christchurch, New Zealand.
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Hiranita T, Kohut SJ, Soto PL, Tanda G, Kopajtic TA, Katz JL. Preclinical efficacy of N-substituted benztropine analogs as antagonists of methamphetamine self-administration in rats. J Pharmacol Exp Ther 2014; 348:174-91. [PMID: 24194527 PMCID: PMC3868882 DOI: 10.1124/jpet.113.208264] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 11/04/2013] [Indexed: 01/16/2023] Open
Abstract
Atypical dopamine-uptake inhibitors have low abuse potential and may serve as leads for development of cocaine-abuse treatments. Among them, the benztropine (BZT) derivatives, N-butyl (JHW007), N-allyl (AHN2-005), and N-methyl (AHN1-055) analogs of 3α-[bis(4'-fluorophenyl)methoxy]-tropane dose-dependently decreased cocaine self-administration without effects on food-maintained responding. Our study examined selectivity by assessing their effects on self-administration of other drugs. As with cocaine, each BZT analog (1.0-10.0 mg/kg i.p.) dose-dependently decreased maximal self-administration of d-methamphetamine (0.01-0.32 mg/kg/infusion) but was inactive against heroin (1.0-32.0 µg/kg/infusion) and ketamine (0.032-1.0 mg/kg/infusion) self-administration. Further, standard dopamine indirect-agonists [WIN35,428 ((-)-3β-(4-fluorophenyl)-tropan-2-β-carboxylic acid methyl ester tartrate), d-amphetamine (0.1-1.0 mg/kg i.p., each)] dose-dependently left-shifted self-administration dose-effect curves for d-methamphetamine, heroin, and ketamine. Noncompetitive NMDA-glutamate receptor/channel antagonists [(+)-MK-801 (0.01-0.1 mg/kg i.p.), memantine (1.0-10.0 mg/kg i.p.)] also left-shifted dose-effect curves for d-methamphetamine and ketamine (but not heroin) self-administration. The µ-agonists [dl-methadone and morphine (1.0-10.0 mg/kg i.p., each)] dose-dependently decreased maximal self-administration of µ-agonists (heroin, remifentanil) but not d-methamphetamine or ketamine self-administration. The µ-agonist-induced decreases were similar to the effects of BZT analogs on stimulant self-administration and effects of food prefeeding on responding maintained by food reinforcement. Radioligand-binding and behavioral studies suggested that inhibition of dopamine transporters and σ receptors were critical for blocking stimulant self-administration by BZT-analogs. Thus, the present results suggest that the effects of BZT analogs on stimulant self-administration are similar to effects of µ-agonists on µ-agonist self-administration and food prefeeding on food-reinforced responding, which implicates behavioral mechanisms for these effects and further supports development of atypical dopamine uptake inhibitors as medications for stimulant abuse.
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Affiliation(s)
- Takato Hiranita
- Psychobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland (T.H., S.J.K., G.T., T.A.K., J.L.K.); Division of Behavioral Biology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland (P.L.S.)
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Wigestrand M, Stenberg M, Walaas S, Fonnum F, Andersson P. Non-dioxin-like PCBs inhibit [3H]WIN-35,428 binding to the dopamine transporter: A structure–activity relationship study. Neurotoxicology 2013; 39:18-24. [DOI: 10.1016/j.neuro.2013.07.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 07/24/2013] [Accepted: 07/24/2013] [Indexed: 11/29/2022]
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Desai RI, Grandy DK, Lupica CR, Katz JL. Pharmacological characterization of a dopamine transporter ligand that functions as a cocaine antagonist. J Pharmacol Exp Ther 2013; 348:106-15. [PMID: 24194528 DOI: 10.1124/jpet.113.208538] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An N-butyl analog of benztropine, JHW007 [N-(n-butyl)-3α-[bis(4'-fluorophenyl)methoxy]-tropane], binds to dopamine transporters (DAT) but has reduced cocaine-like behavioral effects and antagonizes various effects of cocaine. The present study further examined mechanisms underlying these effects. Cocaine dose-dependently increased locomotion, whereas JHW007 was minimally effective but increased activity 24 hours after injection. JHW007 (3-10 mg/kg) dose-dependently and fully antagonized the locomotor-stimulant effects of cocaine (5-60 mg/kg), whereas N-methyl and N-allyl analogs and the dopamine (DA) uptake inhibitor GBR12909 [1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine dihydrochloride] stimulated activity and failed to antagonize effects of cocaine. JHW007 also blocked the locomotor-stimulant effects of the DAT inhibitor GBR12909 but not stimulation produced by the δ-opioid agonist SNC 80 [4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide], which increases activity through nondopaminergic mechanisms. JHW007 blocked locomotor-stimulant effects of cocaine in both DA D2- and CB1-receptor knockout and wild-type mice, indicating a lack of involvement of these targets. Furthermore, JHW007 blocked effects of cocaine on stereotyped rearing but enhanced stereotyped sniffing, suggesting that interference with locomotion by enhanced stereotypies is not responsible for the cocaine-antagonist effects of JHW007. Time-course data indicate that administration of JHW007 antagonized the locomotor-stimulant effects of cocaine within 10 minutes of injection, whereas occupancy at the DAT, as determined in vivo, did not reach a maximum until 4.5 hours after injection. The σ1-receptor antagonist BD 1008 [N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine dihydrobromide] blocked the locomotor-stimulant effects of cocaine. Overall, these findings suggest that JHW007 has cocaine-antagonist effects that are deviate from its DAT occupancy and that some other mechanism, possibly σ-receptor antagonist activity, may contribute to the cocaine-antagonist effect of JHW007 and like drugs.
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Affiliation(s)
- Rajeev I Desai
- Psychobiology Section (R.I.D., J.L.K.) and Electrophysiology Research Section (C.R.L.), National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland; and Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon (D.K.G.)
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Tanda G, Li SM, Mereu M, Thomas AM, Ebbs AL, Chun LE, Tronci V, Green JL, Zou MF, Kopajtic TA, Newman AH, Katz JL. Relations between stimulation of mesolimbic dopamine and place conditioning in rats produced by cocaine or drugs that are tolerant to dopamine transporter conformational change. Psychopharmacology (Berl) 2013; 229:307-21. [PMID: 23612854 PMCID: PMC3758386 DOI: 10.1007/s00213-013-3109-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 04/05/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Dopamine transporter (DAT) conformation plays a role in the effectiveness of cocaine-like and other DAT inhibitors. Cocaine-like stimulants are intolerant to DAT conformation changes having decreased potency in cells transfected with DAT constructs that face the cytosol compared to wild-type DAT. In contrast, analogs of benztropine (BZT) are among compounds that are less affected by DAT conformational change. METHODS We compared the displacement of radioligand binding to various mammalian CNS sites, acute stimulation of accumbens shell dopamine levels, and place conditioning in rats among cocaine and four BZT analogs with Cl substitutions on the diphenyl-ether system including two with carboalkoxy substitutions at the 2-position of the tropane ring. RESULTS Binding assays confirmed high-affinity and selectivity for the DAT with the BZT analogs which also produced significant stimulation of mesolimbic dopamine efflux. Because BZT analogs produced temporal patterns of extracellular dopamine levels different from those by cocaine (3-10 mg/kg, i.p.), the place conditioning produced by BZT analogs and cocaine was compared at doses and times at which both the increase in dopamine levels and rates of increase were similar to those produced by an effective dose of cocaine. Despite this equilibration, none of the BZT analogs tested produced significant place conditioning. CONCLUSIONS The present results extend previous findings suggesting that cocaine-like actions are dependent on a binding equilibrium that favors the outward conformational state of the DAT. In contrast, BZT analogs with reduced dependence on DAT conformation have reduced cocaine-like behavioral effects and may prove useful in development of medications for stimulant abuse.
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Affiliation(s)
- Gianluigi Tanda
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Su Min Li
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Maddalena Mereu
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Alexandra M. Thomas
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Aaron L. Ebbs
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | | | - Valeria Tronci
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Jennifer L. Green
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Mu-Fa Zou
- Medicinal Chemistry Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Theresa A. Kopajtic
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Amy Hauck Newman
- Medicinal Chemistry Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
| | - Jonathan L. Katz
- Psychobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health; 251 Bayview Blvd., NIDA suite 200, Baltimore, MD, 21224
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Velázquez-Sánchez C, García-Verdugo JM, Murga J, Canales JJ. The atypical dopamine transport inhibitor, JHW 007, prevents amphetamine-induced sensitization and synaptic reorganization within the nucleus accumbens. Prog Neuropsychopharmacol Biol Psychiatry 2013; 44:73-80. [PMID: 23385166 DOI: 10.1016/j.pnpbp.2013.01.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 01/25/2013] [Accepted: 01/25/2013] [Indexed: 11/17/2022]
Abstract
Benztropine (BZT) analogs, a family of agents with high affinity for the dopamine transporter have been postulated as potential treatments in stimulant abuse due to their ability to attenuate a wide range of effects evoked by psychomotor stimulants such as cocaine and amphetamine (AMPH). Repeating administration of drugs, including stimulants, can result in behavioral sensitization, a progressive increase in their psychomotor activating effects. We examined in mice the sensitizing effects and the neuroplasticity changes elicited by chronic AMPH exposure, and the modulation of these effects by the BZT derivative and atypical dopamine uptake inhibitor, JHW007, a candidate medication for stimulant abuse. The results indicated that JHW007 did not produce sensitized locomotor activity when given alone but prevented the sensitized motor behavior induced by chronic AMPH administration. Morphological analysis of medium spiny neurons of the nucleus accumbens revealed that JHW 007 prevented the neuroadaptations induced by chronic AMPH exposure, including increments in dendritic arborization, lengthening of dendritic processes and increases in spine density. Furthermore, data revealed that AMPH produced an increase in the density of asymmetric, possibly glutamatergic synapses in the nucleus accumbens, an effect that was also blocked by JHW007 pretreatment. The present observations demonstrate that JHW007 is able to prevent not only AMPH-induced behavioral sensitization but also the long-term structural changes induced by chronic AMPH in the nucleus accumbens. Such findings support the development and evaluation of BZT derivatives as possible leads for treatment in stimulant addiction.
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Affiliation(s)
- Clara Velázquez-Sánchez
- Behavioural Neuroscience, Department of Psychology, University of Canterbury, Christchurch, New Zealand
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Broderick PA, Rosenbaum T. Sex-specific brain deficits in auditory processing in an animal model of cocaine-related schizophrenic disorders. Brain Sci 2013; 3:504-20. [PMID: 24961412 PMCID: PMC4061862 DOI: 10.3390/brainsci3020504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 03/04/2013] [Accepted: 03/20/2013] [Indexed: 11/16/2022] Open
Abstract
Cocaine is a psychostimulant in the pharmacological class of drugs called Local Anesthetics. Interestingly, cocaine is the only drug in this class that has a chemical formula comprised of a tropane ring and is, moreover, addictive. The correlation between tropane and addiction is well-studied. Another well-studied correlation is that between psychosis induced by cocaine and that psychosis endogenously present in the schizophrenic patient. Indeed, both of these psychoses exhibit much the same behavioral as well as neurochemical properties across species. Therefore, in order to study the link between schizophrenia and cocaine addiction, we used a behavioral paradigm called Acoustic Startle. We used this acoustic startle paradigm in female versus male Sprague-Dawley animals to discriminate possible sex differences in responses to startle. The startle method operates through auditory pathways in brain via a network of sensorimotor gating processes within auditory cortex, cochlear nuclei, inferior and superior colliculi, pontine reticular nuclei, in addition to mesocorticolimbic brain reward and nigrostriatal motor circuitries. This paper is the first to report sex differences to acoustic stimuli in Sprague-Dawley animals (Rattus norvegicus) although such gender responses to acoustic startle have been reported in humans (Swerdlow et al. 1997 [1]). The startle method monitors pre-pulse inhibition (PPI) as a measure of the loss of sensorimotor gating in the brain's neuronal auditory network; auditory deficiencies can lead to sensory overload and subsequently cognitive dysfunction. Cocaine addicts and schizophrenic patients as well as cocaine treated animals are reported to exhibit symptoms of defective PPI (Geyer et al., 2001 [2]). Key findings are: (a) Cocaine significantly reduced PPI in both sexes. (b) Females were significantly more sensitive than males; reduced PPI was greater in females than in males. (c) Physiological saline had no effect on startle in either sex. Thus, the data elucidate gender-specificity to the startle response in animals. Finally, preliminary studies show the effect of cocaine on acoustic startle in tandem with effects on estrous cycle. The data further suggest that hormones may play a role in these sex differences to acoustic startle reported herein.
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Affiliation(s)
- Patricia A Broderick
- Department of Physiology, Pharmacology & Neuroscience, The Sophie Davis School of Biomedical Education, The City College of New York, The City University of New York, New York, NY 10031, USA.
| | - Taylor Rosenbaum
- School of Arts and Sciences, Emory University, Atlanta, GA 30322, USA.
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24
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Schmitt KC, Rothman RB, Reith MEA. Nonclassical pharmacology of the dopamine transporter: atypical inhibitors, allosteric modulators, and partial substrates. J Pharmacol Exp Ther 2013; 346:2-10. [PMID: 23568856 DOI: 10.1124/jpet.111.191056] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The dopamine transporter (DAT) is a sodium-coupled symporter protein responsible for modulating the concentration of extraneuronal dopamine in the brain. The DAT is a principle target of various psychostimulant, nootropic, and antidepressant drugs, as well as certain drugs used recreationally, including the notoriously addictive stimulant cocaine. DAT ligands have traditionally been divided into two categories: cocaine-like inhibitors and amphetamine-like substrates. Whereas inhibitors block monoamine uptake by the DAT but are not translocated across the membrane, substrates are actively translocated and trigger DAT-mediated release of dopamine by reversal of the translocation cycle. Because both inhibitors and substrates increase extraneuronal dopamine levels, it is often assumed that all DAT ligands possess an addictive liability equivalent to that of cocaine. However, certain recently developed ligands, such as atypical benztropine-like DAT inhibitors with reduced or even a complete lack of cocaine-like rewarding effects, suggest that addictiveness is not a constant property of DAT-affecting compounds. These atypical ligands do not conform to the classic preconception that all DAT inhibitors (or substrates) are functionally and mechanistically alike. Instead, they suggest the possibility that the DAT exhibits some of the ligand-specific pleiotropic functional qualities inherent to G-protein-coupled receptors. That is, ligands with different chemical structures induce specific conformational changes in the transporter protein that can be differentially transduced by the cell, ultimately eliciting unique behavioral and psychological effects. The present overview discusses compounds with conformation-specific activity, useful not only as tools for studying the mechanics of dopamine transport, but also as leads for medication development in addictive disorders.
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Affiliation(s)
- Kyle C Schmitt
- Department of Neurosurgery, New York University School of Medicine, 455 First Ave., Public Health Laboratories (8th Floor), New York, New York 10016, USA.
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The atypical stimulant and nootropic modafinil interacts with the dopamine transporter in a different manner than classical cocaine-like inhibitors. PLoS One 2011; 6:e25790. [PMID: 22043293 PMCID: PMC3197159 DOI: 10.1371/journal.pone.0025790] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 09/11/2011] [Indexed: 11/19/2022] Open
Abstract
Modafinil is a mild psychostimulant with pro-cognitive and antidepressant effects. Unlike many conventional stimulants, modafinil has little appreciable potential for abuse, making it a promising therapeutic agent for cocaine addiction. The chief molecular target of modafinil is the dopamine transporter (DAT); however, the mechanistic details underlying modafinil's unique effects remain unknown. Recent studies suggest that the conformational effects of a given DAT ligand influence the magnitude of the ligand's reinforcing properties. For example, the atypical DAT inhibitors benztropine and GBR12909 do not share cocaine's notorious addictive liability, despite having greater binding affinity. Here, we show that the binding mechanism of modafinil is different than cocaine and similar to other atypical inhibitors. We previously established two mutations (W84L and D313N) that increase the likelihood that the DAT will adopt an outward-facing conformational state—these mutations increase the affinity of cocaine-like inhibitors considerably, but have little or opposite effect on atypical inhibitor binding. Thus, a compound's WT/mutant affinity ratio can indicate whether the compound preferentially interacts with a more outward- or inward-facing conformational state. Modafinil displayed affinity ratios similar to those of benztropine, GBR12909 and bupropion (which lack cocaine-like effects in humans), but far different than those of cocaine, β-CFT or methylphenidate. Whereas treatment with zinc (known to stabilize an outward-facing transporter state) increased the affinity of cocaine and methylphenidate two-fold, it had little or no effect on the binding of modafinil, benztropine, bupropion or GBR12909. Additionally, computational modeling of inhibitor binding indicated that while β-CFT and methylphenidate stabilize an “open-to-out” conformation, binding of either modafinil or bupropion gives rise to a more closed conformation. Our findings highlight a mechanistic difference between modafinil and cocaine-like stimulants and further demonstrate that the conformational effects of a given DAT inhibitor influence its phenomenological effects.
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Li SM, Kopajtic TA, O'Callaghan MJ, Agoston GE, Cao J, Newman AH, Katz JL. N-substituted benztropine analogs: selective dopamine transporter ligands with a fast onset of action and minimal cocaine-like behavioral effects. J Pharmacol Exp Ther 2010; 336:575-85. [PMID: 21088247 DOI: 10.1124/jpet.110.173260] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Previous studies suggested that differences between the behavioral effects of cocaine and analogs of benztropine were related to the relatively slow onset of action of the latter compounds. Several N-substituted benztropine analogs with a relatively fast onset of effects were studied to assess whether a fast onset of effects would render the effects more similar to those of cocaine. Only one of the compounds increased locomotor activity, and the increases were modest compared with those of 10 to 20 mg/kg cocaine. In rats trained to discriminate 10 mg/kg cocaine from saline none of the compounds produced more than 40% cocaine-like responds up to 2 h after injection. None of the compounds produced place-conditioning when examined up to 90 min after injection, indicating minimal abuse liability. The compounds had 5.6 to 30 nM affinities at the dopamine transporter (DAT), with uniformly lower affinities at norepinephrine and serotonin transporters (from 490-4600 and 1420-7350 nM, respectively). Affinities at muscarinic M(1) receptors were from 100- to 300-fold lower than DAT affinities, suggesting minimal contribution of those sites to the behavioral effects of the compounds. Affinities at histaminic H(1) sites were from 11- to 43-fold lower than those for the DAT. The compounds also had affinity for sigma, 5-hydroxytryptamine(1) (5-HT(1)), and 5-HT(2) receptors that may have contributed to their behavioral effects. Together, the results indicate that a slow onset of action is not a necessary condition for reduced cocaine-like effects of atypical DAT ligands and suggest several mechanisms that may contribute to the reduced cocaine-like efficacy of these compounds.
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Affiliation(s)
- Su-Min Li
- Sections, Medications Discovery Research Branch, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, Maryland 21224, USA
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