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Frie JA, McCunn P, Eed A, Hassan A, Luciani KR, Chen C, Tyndale RF, Khokhar JY. Factors influencing JUUL e-cigarette nicotine vapour-induced reward, withdrawal, pharmacokinetics and brain connectivity in rats: sex matters. Neuropsychopharmacology 2024; 49:782-795. [PMID: 38057369 PMCID: PMC10948865 DOI: 10.1038/s41386-023-01773-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 11/05/2023] [Accepted: 11/14/2023] [Indexed: 12/08/2023]
Abstract
Though vaping likely represents a safer alternative to smoking, it is not without risks, many of which are not well understood, especially for vulnerable populations. Here we evaluate the sex- and age-dependent effects of JUUL nicotine vapour in rats. Following passive nicotine vapour exposures (from 59 mg/ml JUUL nicotine pods), rats were evaluated for reward-like behaviour, locomotion, and precipitated withdrawal. Pharmacokinetics of nicotine and its metabolites in brain and plasma and the long-term impact of nicotine vapour exposure on functional magnetic resonance imaging-based brain connectivity were assessed. Adult female rats acquired conditioned place preference (CPP) at a high dose (600 s of exposure) of nicotine vapour while female adolescents, as well as male adults and adolescents did not. Adult and adolescent male rats displayed nicotine vapour-induced precipitated withdrawal and hyperlocomotion, while both adult and adolescent female rats did not. Adult females showed higher venous and arterial plasma and brain nicotine and nicotine metabolite concentrations compared to adult males and adolescent females. Adolescent females showed higher brain nicotine concentration compared to adolescent males. Both network-based statistics and between-component group connectivity analyses uncovered reduced connectivity in nicotine-exposed rats, with a significant group by sex interaction observed in both analyses. The short- and long-term effects of nicotine vapour are affected by sex and age, with distinct behavioural, pharmacokinetic, and altered network connectivity outcomes dependent on these variables.
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Affiliation(s)
- Jude A Frie
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Patrick McCunn
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Amr Eed
- Department of Medical Biophysics and Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Ahmad Hassan
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Karling R Luciani
- Department of Psychiatry, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Chuyun Chen
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Rachel F Tyndale
- Departments of Psychiatry, and Pharmacology & Toxicology, University of Toronto, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Jibran Y Khokhar
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
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Wang X, Chen Y, Dong J, Ge J, Liu X, Liu J. Neurobiology of Stress-Induced Nicotine Relapse. Int J Mol Sci 2024; 25:1482. [PMID: 38338760 PMCID: PMC10855331 DOI: 10.3390/ijms25031482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 01/15/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
Tobacco smoking is the leading cause of preventable death and disease. Although there are some FAD-approved medicines for controlling smoking, the relapse rate remains very high. Among the factors that could induce nicotine relapse, stress might be the most important one. In the last decades, preclinical studies have generated many new findings that lead to a better understanding of stress-induced relapse of nicotine-seeking. Several molecules such as α3β4 nicotinic acetylcholine receptor, α2-adrenergic receptors, cannabinoid receptor 1, trace amine-associated receptor 1, and neuropeptide systems (corticotropin-releasing factor and its receptors, dynorphine and kappa opioid receptor) have been linked to stress-induced nicotine relapse. In this review, we discuss recent advances in the neurobiology, treatment targets, and potential therapeutics of stress-induced nicotine relapse. We also discuss some factors that may influence stress-induced nicotine relapse and that should be considered in future studies. In the final section, a perspective on some research directions is provided. Further investigation on the neurobiology of stress-induced nicotine relapse will shed light on the development of new medicines for controlling smoking and will help us understand the interactions between the stress and reward systems in the brain.
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Affiliation(s)
| | | | | | | | | | - Jianfeng Liu
- Institute of Brain Science and Advanced Technology, Hubei Province Key Laboratory of Occupational Hazard Identification and Control, School of Medicine, Wuhan University of Science and Technology, Wuhan 430065, China (Y.C.); (J.D.)
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Kim K, Picciotto MR. Nicotine addiction: More than just dopamine. Curr Opin Neurobiol 2023; 83:102797. [PMID: 37832393 PMCID: PMC10842238 DOI: 10.1016/j.conb.2023.102797] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 10/15/2023]
Abstract
Despite decades of research and anti-tobacco messaging, nicotine addiction remains an important public health problem leading to hundreds of thousands of deaths each year. While fundamental studies have identified molecular, circuit-level and behavioral mechanisms important for nicotine reinforcement and withdrawal, recent studies have identified additional pathways that are important for both nicotine seeking and aversion. In particular, although dopaminergic mechanisms are necessary for nicotine-dependent reward and drug-seeking, novel glutamate and GABA signaling mechanisms in the mesolimbic system have been identified for their contributions to reward-related behaviors. An additional area of active investigation for nicotine addiction focuses on molecular mechanisms in the habenula-interpeduncular pathway driving nicotine aversion and withdrawal. Across all these domains, sex differences in the molecular basis of nicotine-induced behaviors have emerged that identify important new directions for future research. Recent studies reviewed here highlight additional pathways that could provide therapeutic targets for smoking cessation and problematic nicotine vaping.
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Affiliation(s)
- Kristen Kim
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA; Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA. https://twitter.com/kristenkim415
| | - Marina R Picciotto
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA; Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA.
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Krishnan S, Bevins RA, de Wit H. Place conditioning in humans: opportunities for translational research. Psychopharmacology (Berl) 2023; 240:2221-2230. [PMID: 36656336 PMCID: PMC10949408 DOI: 10.1007/s00213-023-06316-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 01/08/2023] [Indexed: 01/20/2023]
Abstract
RATIONALE Translational research, especially research that bridges studies with humans and nonhuman species, is critical to advancing our understanding of human disorders such as addiction. This advancement requires reliable and rigorous models to study the underlying constructs contributing to the maladaptive behavior. OBJECTIVE In this commentary, we address some of the challenges of conducting translational research by examining a single procedure, place conditioning. Place conditioning is commonly used with laboratory animals to study the conditioned rewarding effects of drugs, and recent studies indicate that a similar procedure can be used in humans. RESULTS We discuss the opportunities and challenges of making the procedure comparable across species, as well as discuss the benefits of more systematically applying the procedure to humans. CONCLUSION We argue that the capacity of humans to report verbally on their internal experiences (perceptions, affective states, likes and dislikes) add an important dimension to the understanding of the procedures used in laboratory animals.
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Affiliation(s)
- Seetha Krishnan
- Department of Neurobiology and Institute for Neuroscience, University of Chicago, Chicago, IL, 60637, USA
| | - Rick A Bevins
- Department of Psychology, University of Nebraska - Lincoln, Lincoln, NE, 68588-0308, USA
| | - Harriet de Wit
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, Chicago, IL, 60637, USA.
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Avelar AJ, Cooper SY, Wright TD, Wright SK, Richardson MR, Henderson BJ. Morphine Exposure Reduces Nicotine-Induced Upregulation of Nicotinic Receptors and Decreases Volitional Nicotine Intake in a Mouse Model. Nicotine Tob Res 2022; 24:1161-1168. [PMID: 34999827 PMCID: PMC9278828 DOI: 10.1093/ntr/ntac002] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 10/18/2021] [Accepted: 01/04/2022] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Nicotine addiction remains a primary health concern as tobacco smoking remains the number one cause of preventable death in America. At the same time, America is still facing the threat of the opioid epidemic. While the prevalence of smoking combustible cigarettes or electronic nicotine delivery systems in the United States varies between 12% and 35%, the smoking rates among the opioid use dependent (OUD) population is 74%-97%. We examined changes in brain reward mechanisms in which co-use of nicotine and opioids may result in enhanced reward and reinforcement. AIMS AND METHODS Adult male and female α4-mCherryα6-GFP mice (C57BL/6J) were used in conditioned place preference (CPP) and microscopy assays to examine reward-related behavior and nicotinic acetylcholine receptor (nAChR) upregulation following treatments with saline, nicotine, morphine, or nicotine plus morphine. Following this, separate mice were trained in e-Vape self-administration assays to examine morphine's impact on nicotine reinforcement. RESULTS We observed that nicotine and morphine coexposure in a CPP assay did not produce enhanced reward-related behavior when compared with nicotine or morphine alone. In parallel we observed coexposure reduced nicotine-induced upregulation of nAChRs on ventral tegmental area dopamine and GABA neurons. Additionally, we observed that concurrent morphine exposure reduced nicotine (plus menthol) vapor self-administration in male and female mice. CONCLUSIONS While nicotine use is high among OUD individuals, our CPP assays suggest coexposure not only fails to enhance reward-related behavior but also reduces nicotine-induced changes in ventral tegmental area neurobiology. Our self-administration assays suggest that morphine exposure during nicotine acquisition reduces nicotine reinforcement-related behavior. IMPLICATIONS While some may postulate that the co-use of opioids and nicotine may be driven by reward-related mechanisms, our data indicate that opioid exposure may hinder nicotine intake due to reduced upregulation of nAChRs critical for nicotine reward and reinforcement. Thus, the high co-use in OUD individuals may be a result of other mechanisms and this warrants further investigations into nicotine and opioid co-use.
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Affiliation(s)
- Alicia J Avelar
- Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, Huntington, WV, USA
| | - Skylar Y Cooper
- Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, Huntington, WV, USA
| | - Thomas Douglas Wright
- Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, Huntington, WV, USA
| | - Sheavonnie K Wright
- Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, Huntington, WV, USA
| | - Montana R Richardson
- Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, Huntington, WV, USA
| | - Brandon J Henderson
- Corresponding Author: Brandon J. Henderson, PhD, Department of Biomedical Sciences, Joan C Edwards School of Medicine at Marshall University, 1700 3rd Ave, 410 BBSC, Huntington, WV 25703, USA. Telephone: 304-696-7316; Fax: 304-696-7391; E-mail:
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Chellian R, Behnood-Rod A, Wilson R, Bruijnzeel AW. Rewarding Effects of Nicotine Self-administration Increase Over Time in Male and Female Rats. Nicotine Tob Res 2021; 23:2117-2126. [PMID: 33987656 DOI: 10.1093/ntr/ntab097] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 05/11/2021] [Indexed: 11/14/2022]
Abstract
INTRODUCTION Smoking and the use of other nicotine-containing products is rewarding in humans. The self-administration of nicotine is also rewarding in male rats. However, it is unknown if there are sex differences in the reward-enhancing effects of nicotine self-administration and if the rewarding effects of nicotine change over time. METHODS Rats were prepared with catheters and intracranial self-stimulation (ICSS) electrodes to investigate the effects of nicotine and saline self-administration on reward function. A decrease in thresholds in the ICSS procedure reflects an enhancement of reward function. The ICSS parameters were determined before and after the self-administration sessions from days 1 to 10, and after the self-administration sessions from days 11 to 15. RESULTS During the first 10 days, there was no sex difference in nicotine intake, but during the last 5 days, the females took more nicotine than the males. During the first 10 days, nicotine self-administration did not lower the brain reward thresholds but decreased the response latencies. During the last 5 days, nicotine lowered the reward thresholds and decreased the response latencies. An analysis with the 5-day averages (days 1-5, 6-10, and 11-15) showed that the reward enhancing and stimulatory effects of nicotine increased over time. There were no sex differences in the reward-enhancing and stimulatory effects of nicotine. The nicotinic receptor antagonist mecamylamine diminished the reward-enhancing and stimulatory effects of nicotine. CONCLUSION These findings indicate that the rewarding effects of nicotine self-administration increase over time, and there are no sex differences in the reward-enhancing effects of nicotine self-administration in rats. IMPLICATIONS This study investigated the rewarding effect of nicotine and saline self-administration in male and female rats. The self-administration of nicotine, but not saline, enhanced brain reward function and had stimulatory effects. The rewarding effects of nicotine increased over time in the males and the females. Despite that the females had a higher level of nicotine intake than the males, the reward-enhancing effects of nicotine self-administration were the same. These findings suggest that in new tobacco and e-cigarette users, nicotine's rewarding effects might increase quickly, and a higher level of nicotine use in females might not translate into greater rewarding effects.
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Affiliation(s)
| | - Azin Behnood-Rod
- Department of Psychiatry, University of Florida, Gainesville, FL, USA
| | - Ryann Wilson
- Department of Psychiatry, University of Florida, Gainesville, FL, USA
| | - Adriaan W Bruijnzeel
- Department of Psychiatry, University of Florida, Gainesville, FL, USA.,Department of Neuroscience, University of Florida, Gainesville, FL, USA
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Lee AM, Mansuri MS, Wilson RS, Lam TT, Nairn AC, Picciotto MR. Sex Differences in the Ventral Tegmental Area and Nucleus Accumbens Proteome at Baseline and Following Nicotine Exposure. Front Mol Neurosci 2021; 14:657064. [PMID: 34335180 PMCID: PMC8317211 DOI: 10.3389/fnmol.2021.657064] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 06/09/2021] [Indexed: 12/20/2022] Open
Abstract
Sex differences in behaviors relevant to nicotine addiction have been observed in rodent models and human subjects. Behavioral, imaging, and epidemiological studies also suggest underlying sex differences in mesolimbic dopamine signaling pathways. In this study we evaluated the proteome in the ventral tegmental area (VTA) and nucleus accumbens (NAc) shell in male and female mice. Experimental groups included two mouse strains (C3H/HeJ and C57BL/6J) at baseline, a sub-chronic, rewarding regimen of nicotine in C3H/HeJ mice, and chronic nicotine administration and withdrawal in C57BL/6J mice. Isobaric labeling with a TMT 10-plex system, sample fractionation, and tandem mass spectrometry were used to quantify changes in protein abundance. In C3H/HeJ mice, similar numbers of proteins were differentially regulated between sexes at baseline compared with within each sex after sub-chronic nicotine administration. In C57BL/6J mice, there were significantly greater numbers of proteins differentially regulated between sexes at baseline compared with within each sex after chronic nicotine administration and withdrawal. Despite differences by sex, strain, and nicotine exposure parameters, glial fibrillary acidic protein (GFAP) and dopamine and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32, Ppp1r1b) were repeatedly identified as significantly altered proteins, especially in the VTA. Further, network analyses showed sex- and nicotine-dependent regulation of a number of signaling pathways, including dopaminergic signaling. Sub-chronic nicotine exposure in female mice increased proteins related to dopaminergic signaling in the NAc shell but decreased them in the VTA, whereas the opposite pattern was observed in male mice. In contrast, dopaminergic signaling pathways were similarly upregulated in both male and female VTA after chronic nicotine and withdrawal. Overall, this study identifies significant sex differences in the proteome of the mesolimbic system, at baseline and after nicotine reward or withdrawal, which may help explain differential trajectories and susceptibility to nicotine addiction in males and females.
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Affiliation(s)
- Angela M Lee
- Department of Psychiatry, Yale University, New Haven, CT, United States.,Yale Interdepartmental Neuroscience Program, New Haven, CT, United States
| | - Mohammad Shahid Mansuri
- Yale/NIDA Neuroproteomics Center, New Haven, CT, United States.,Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, United States
| | - Rashaun S Wilson
- Yale/NIDA Neuroproteomics Center, New Haven, CT, United States.,Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, United States.,W.M Keck Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT, United States
| | - TuKiet T Lam
- Yale/NIDA Neuroproteomics Center, New Haven, CT, United States.,Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, United States.,W.M Keck Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT, United States
| | - Angus C Nairn
- Department of Psychiatry, Yale University, New Haven, CT, United States.,Yale/NIDA Neuroproteomics Center, New Haven, CT, United States
| | - Marina R Picciotto
- Department of Psychiatry, Yale University, New Haven, CT, United States.,Yale Interdepartmental Neuroscience Program, New Haven, CT, United States
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Lee AM, Picciotto MR. Effects of nicotine on DARPP-32 and CaMKII signaling relevant to addiction. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2020; 90:89-115. [PMID: 33706940 PMCID: PMC8008986 DOI: 10.1016/bs.apha.2020.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Paul Greengard brought to neuroscience the idea of, and evidence for, the role of second messenger systems in neuronal signaling. The fundamental nature of his contributions is evident in the far reach of his work, relevant to various subfields and topics in neuroscience. In this review, we discuss some of Greengard's work from the perspective of nicotinic acetylcholine receptors and their relevance to nicotine addiction. Specifically, we review the roles of dopamine- and cAMP-regulated phospho-protein of 32kDa (DARPP-32) and Ca2+/calmodulin-dependent kinase II (CaMKII) in nicotine-dependent behaviors. For each protein, we discuss the historical context of their discovery and initial characterization, focusing on the extensive biochemical and immunohistochemical work conducted by Greengard and colleagues. We then briefly summarize contemporary understanding of each protein in key intracellular signaling cascades and evidence for the role of each protein with respect to systems and behaviors relevant to nicotine addiction.
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Affiliation(s)
- Angela M Lee
- Department of Psychiatry, Yale University, New Haven, CT, United States; Yale Interdepartmental Neuroscience Program, New Haven, CT, United States
| | - Marina R Picciotto
- Department of Psychiatry, Yale University, New Haven, CT, United States; Yale Interdepartmental Neuroscience Program, New Haven, CT, United States.
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Green Apple e-Cigarette Flavorant Farnesene Triggers Reward-Related Behavior by Promoting High-Sensitivity nAChRs in the Ventral Tegmental Area. eNeuro 2020; 7:ENEURO.0172-20.2020. [PMID: 32747456 PMCID: PMC7433896 DOI: 10.1523/eneuro.0172-20.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/04/2020] [Accepted: 06/11/2020] [Indexed: 11/21/2022] Open
Abstract
While combustible cigarette smoking has declined, the use of electronic nicotine delivery systems (ENDS) has increased. ENDS are popular among adolescents, and chemical flavorants are an increasing concern because of the growing use of zero-nicotine flavored e-liquids. Despite this, little is known regarding the effects of ENDS flavorants on vaping-related behavior. Following previous studies demonstrating the green apple flavorant, farnesol, enhances nicotine reward and exhibits rewarding properties without nicotine, this work focuses on the green apple flavorant, farnesene, for its impact on vaping-related behaviors. Using adult C57BL/6J mice, genetically modified to contain fluorescent nicotinic acetylcholine receptors (nAChRs), and farnesene doses of 0.1, 1.0, and 10 mg/kg, we observed farnesene-alone produces reward-related behavior in both male and female mice. We then performed whole-cell patch-clamp electrophysiology and observed farnesene-induced inward currents in ventral tegmental area (VTA) putative dopamine (pDA) neurons that were blocked by the nAChR antagonist, DhβE. While the amplitudes of farnesene-induced currents are ∼30% of nicotine's efficacy, this indicates the potential for some ENDS flavorants to stimulate nAChR function. Additionally, farnesene enhances nicotine's potency for activating nAChRs on VTA dopamine neurons. This may be because of changes in nAChR stoichiometry as our data suggest a shift toward high-sensitivity α4β2 nAChRs. Consequently, these data show that the green apple flavorant, farnesene, causes reward-related behavior without nicotine through changes in nAChR stoichiometry that results in an enhanced effect of nicotine on VTA dopamine neurons. These results demonstrate the importance of future investigations into ENDS flavorants and their effects on vaping-related behaviors.
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α 2A-adrenergic heteroreceptors are required for stress-induced reinstatement of cocaine conditioned place preference. Neuropsychopharmacology 2020; 45:1473-1481. [PMID: 32074627 PMCID: PMC7360592 DOI: 10.1038/s41386-020-0641-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/03/2020] [Accepted: 02/10/2020] [Indexed: 02/08/2023]
Abstract
The α2a-adrenergic receptor (α2a-AR) agonist guanfacine has been investigated as a potential treatment for substance use disorders. While decreasing stress-induced reinstatement of cocaine seeking in animal models and stress-induced craving in human studies, guanfacine has not been reported to decrease relapse rates. Although guanfacine engages α2a-AR autoreceptors, it also activates excitatory Gi-coupled heteroreceptors in the bed nucleus of the stria terminalis (BNST), a key brain region in driving stress-induced relapse. Thus, BNST α2a-AR heteroreceptor signaling might decrease the beneficial efficacy of guanfacine. We aimed to determine the role of α2a-AR heteroreceptors and BNST Gi-GPCR signaling in stress-induced reinstatement of cocaine conditioned place preference (CPP) and the effects of low dose guanfacine on BNST activity and stress-induced reinstatement. We used a genetic deletion strategy and the cocaine CPP procedure to first define the contributions of α2a-AR heteroreceptors to stress-induced reinstatement. Next, we mimicked BNST Gi-coupled α2a-AR heteroreceptor signaling using a Gi-coupled designer receptor exclusively activated by designer drug (Gi-DREADD) approach. Finally, we evaluated the effects of low-dose guanfacine on BNST cFOS immunoreactivity and stress-induced reinstatement. We show that α2a-AR heteroreceptor deletion disrupts stress-induced reinstatement and that BNST Gi-DREADD activation is sufficient to induce reinstatement. Importantly, we found that low-dose guanfacine does not increase BNST activity, but prevents stress-induced reinstatement. Our findings demonstrate a role for α2a-AR heteroreceptors and BNST Gi-GPCR signaling in stress-induced reinstatement of cocaine CPP and provide insight into the impact of dose on the efficacy of guanfacine as a treatment for stress-induced relapse of cocaine use.
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