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Smethells JR, S W, P M, MG L, AP H. The role of β-Nicotyrine in E-Cigarette abuse liability I: Drug Discrimination. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.12.603310. [PMID: 39071347 PMCID: PMC11275838 DOI: 10.1101/2024.07.12.603310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Background β-Nicotyrine (β-Nic) is a unique minor alkaloid constituent in electronic nicotine delivery systems (ENDS) that is derived from nicotine (Nic) degradation and can reach 25% of Nic concentrations in ENDS aerosol. β-Nic slows Nic metabolism and prolongs systemic Nic exposure, which may alter the discriminability of Nic. The present study sought to examine β-Nic has interoceptive effects itself, and if it alters the subjective effects ENDS products within a drug-discrimination paradigm. Methods The pharmacodynamics of β-Nic were examined in vitro, and a nicotine discrimination paradigm was used to determine if β-Nic (0 - 5.0 mg/kg) shares discriminative stimulus properties with Nic (0.2 mg/kg) in male (n = 13) and female (n = 14) rats after 10- & 60-min β-Nic pretreatment delays. A second group of rats was trained to discriminate β-Nic and Nornicotine (Nornic) from saline to determine if β-Nic alone has interoceptive properties and whether they are similar to Nornic. Results β-Nic had similar binding affinity and efficacy at the α4β2 nicotinic receptor subtype as Nornic, ~50% of Nic efficacy. However, β-Nic only weakly substituted for Nic during substitution testing in female rats, but not males, whereas Nornic fully substituted for Nic. Combination testing at the 10 and 60-min pretreatment intervals showed that β-Nic dose-dependently increased the duration of nicotine's discriminative stimulus effects, especially at the 60-min delay. Drug naïve rats could reliably discriminate Nornic, but not β-Nic, from Sal. Conclusion β-Nic increased and prolonged the interoceptive stimulus properties of Nic, suggesting it may alter to the abuse liability of ENDS through its ability to slow Nic metabolism.
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Affiliation(s)
- JR Smethells
- Hennepin Healthcare Research Institute, Minneapolis, MN, USA
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Wilde S
- Hennepin Healthcare Research Institute, Minneapolis, MN, USA
| | - Muelken P
- Hennepin Healthcare Research Institute, Minneapolis, MN, USA
| | - LeSage MG
- Hennepin Healthcare Research Institute, Minneapolis, MN, USA
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
- Department of Psychology, University of Minnesota, Minneapolis, MN, USA
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Harris AP
- Hennepin Healthcare Research Institute, Minneapolis, MN, USA
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA
- Department of Psychology, University of Minnesota, Minneapolis, MN, USA
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Smethells JR, Burroughs D, Saykao A, LeSage MG. The relative reinforcing efficacy of nicotine in an adolescent rat model of attention-deficit hyperactivity disorder. Front Psychiatry 2023; 14:1154773. [PMID: 37255676 PMCID: PMC10225533 DOI: 10.3389/fpsyt.2023.1154773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 04/14/2023] [Indexed: 06/01/2023] Open
Abstract
Introduction Attention-deficit/hyperactivity disorder (ADHD) is an independent risk factor for tobacco use disorder. Individuals with ADHD are more likely to begin smoking at a younger age, become a daily smoker sooner, smoke more cigarettes per day, and exhibit greater nicotine dependence than individuals without ADHD. It is unclear whether these findings are due to the reinforcing efficacy of nicotine per se being greater among individuals with ADHD. The purpose of the present study was to examine this issue using an animal model of ADHD, the spontaneously hypertensive rat (SHR) strain. Methods Adolescent SHR and Wistar (control) rats were given access to a typically reinforcing nicotine unit dose (30 μg/kg), a threshold reinforcing nicotine dose (4 μg/kg), or saline under an FR 1 (week 1) and FR 2 (week 2) schedule during 23 h sessions to examine acquisition of self-administration. Behavioral economic demand elasticity was then evaluated at the 30 μg/kg dose through an FR escalation procedure. Results At the 30 μg/kg dose, SHR rats exhibited a lower average response rate, lower mean active to inactive lever discrimination ratio, and lower proportion of rats acquiring self-administration compared to control rats. During demand assessment, SHR rats showed no significant difference from Wistars in demand intensity (Q0) or elasticity (α; i.e., reinforcing efficacy). In addition, no strain difference in acquisition measures were observed at the 4 μg/kg dose. Discussion These findings suggest that the increased risk of tobacco use disorder in adolescents with ADHD may not be attributable to a greater reinforcing efficacy of nicotine, and that other aspects of tobacco smoking (e.g., non-nicotine constituents, sensory factors) may play a more important role. A policy implication of these findings is that a nicotine standard to reduce initiation of tobacco use among adolescents in the general population may also be effective among those with ADHD.
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Affiliation(s)
- John R. Smethells
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States
- Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, United States
| | | | - Amy Saykao
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States
| | - Mark G. LeSage
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States
- Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, United States
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
- Department of Psychology, University of Minnesota, Minneapolis, MN, United States
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Qin X, Hou X, Xu X, Chen L, Gao A, Hao Y, Du X, Zhao L, Shi Y, Li Q. Down-regulation of connexin 43 contributes to structure and function of pulmonary artery in nicotine-administered mice. Toxicol Lett 2023; 377:1-13. [PMID: 36720419 DOI: 10.1016/j.toxlet.2023.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 01/02/2023] [Accepted: 01/20/2023] [Indexed: 01/30/2023]
Abstract
Dysregulated connexin signaling is implicated in the pathophysiology of pulmonary artery hypertension (PAH). Nicotine affects pulmonary vascular remodeling. However, the potential mechanistic link between connexin signaling and nicotine-induced pulmonary artery remodeling remains unclear. We aimed to investigate the role of connexin 43 (Cx43) in pulmonary artery remodeling in nicotine-administered C57BL/6 J wild-type (WT) and Cx43 heterozygous (Cx43+/-) mice. Hemodynamic parameters and right ventricle pathology were assessed in the mice. Serum biochemical indices of hepatic and renal function were measured. The RT-PCR, immunofluorescence, and western blotting were conducted to evaluate Cx43 mRNA and protein levels. We performed histological staining to identify pulmonary arteries. Wire myography was used to examine contraction and relaxation responses in the pulmonary arteries. Pulmonary vascular permeability was assessed through Evans blue staining. Compared with the WT group, the Cx43+/- group showed lower Cx43 mRNA and protein expression in the pulmonary arteries (P < 0.01). Nicotine treatment significantly increased Cx43 expression (P < 0.01) and induced morphological changes in the pulmonary arteries (P < 0.01). Our findings suggest that Cx43 plays a crucial role in pulmonary artery reactivity and permeability in mice. Furthermore, downregulation of Cx43 expression may contribute to alterations in pulmonary artery structure and function.
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Affiliation(s)
- Xiaojiang Qin
- School of Public Health, Shanxi Medical University, 56 Xinjian South Road, Taiyuan 030001, Shanxi, China; China Key Laboratory of Cellular Physiology (Shanxi Medical University), Ministry of Education, China
| | - Xiaomin Hou
- Department of Pharmacology, Shanxi Medical University, Shanxi, China; China Key Laboratory of Cellular Physiology (Shanxi Medical University), Ministry of Education, China
| | - Xinrong Xu
- School of Public Health, Shanxi Medical University, 56 Xinjian South Road, Taiyuan 030001, Shanxi, China
| | - Liangjin Chen
- School of Public Health, Shanxi Medical University, 56 Xinjian South Road, Taiyuan 030001, Shanxi, China
| | - Anqi Gao
- School of Public Health, Shanxi Medical University, 56 Xinjian South Road, Taiyuan 030001, Shanxi, China
| | - Yuxuan Hao
- School of Public Health, Shanxi Medical University, 56 Xinjian South Road, Taiyuan 030001, Shanxi, China
| | - Xufeng Du
- Department of Exercise Rehabilitation, Shanxi Medical University, Shanxi, China
| | - Liangyuan Zhao
- Department of Exercise Rehabilitation, Shanxi Medical University, Shanxi, China
| | - Yiwei Shi
- Department of Respiratory and Critical Care Medicine, Shanxi Medical University Affiliated First Hospital, Shanxi, China.
| | - Qingshan Li
- Shanxi Key Laboratory of Chronic Inflammatory Targeted Drugs, School of Materia Medica, Shanxi University of Traditional Chinese Medicine, 121 University Street, Jinzhong 030602, Shanxi, China.
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Sved AF, Weeks JJ, Grace AA, Smith TT, Donny EC. Monoamine oxidase inhibition in cigarette smokers: From preclinical studies to tobacco product regulation. Front Neurosci 2022; 16:886496. [PMID: 36051642 PMCID: PMC9424897 DOI: 10.3389/fnins.2022.886496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 07/21/2022] [Indexed: 11/13/2022] Open
Abstract
Monoamine oxidase (MAO) activity is reduced in cigarette smokers and this may promote the reinforcing actions of nicotine, thereby enhancing the addictive properties of cigarettes. At present, it is unclear how cigarette smoking leads to MAO inhibition, but preclinical studies in rodents show that MAO inhibition increases nicotine self-administration, especially at low doses of nicotine. This effect of MAO inhibition develops slowly, likely due to plasticity of brain monoamine systems; studies relying on acute MAO inhibition are unlikely to replicate what happens with smoking. Given that MAO inhibition may reduce the threshold level at which nicotine becomes reinforcing, it is important to consider this in the context of very low nicotine content (VLNC) cigarettes and potential tobacco product regulation. It is also important to consider how this interaction between MAO inhibition and the reinforcing actions of nicotine may be modified in populations that are particularly vulnerable to nicotine dependence. In the context of these issues, we show that the MAO-inhibiting action of cigarette smoke extract (CSE) is similar in VLNC cigarettes and cigarettes with a standard nicotine content. In addition, we present evidence that in a rodent model of schizophrenia the effect of MAO inhibition to enhance nicotine self-administration is absent, and speculate how this may relate to brain serotonin systems. These issues are relevant to the MAO-inhibiting effect of cigarette smoking and its implications to tobacco product regulation.
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Affiliation(s)
- Alan F. Sved
- Departments of Neuroscience, Psychiatry and Psychology, University of Pittsburgh, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
- *Correspondence: Alan F. Sved,
| | - Jillian J. Weeks
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
| | - Anthony A. Grace
- Departments of Neuroscience, Psychiatry and Psychology, University of Pittsburgh, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
| | - Tracy T. Smith
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, United States
| | - Eric C. Donny
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, United States
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