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Walker NB, Tucker BR, Thomas LN, Tapp AE, Drenan DR, Drenan RM. Expression of sensitized β2 nAChR subunits in VTA neurons enhances intravenous nicotine self-administration in male rats. Neuropharmacology 2024; 261:110161. [PMID: 39299573 DOI: 10.1016/j.neuropharm.2024.110161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 09/12/2024] [Accepted: 09/13/2024] [Indexed: 09/22/2024]
Abstract
Ventral tegmental area (VTA) nicotinic acetylcholine receptors (nAChRs) are important for nicotine reinforcement. To determine whether and to what extent these receptors are sufficient for nicotine reinforcement, we expressed β2Leu9'Ser (i.e. sensitized) nAChR subunits in the VTA of adult male rats and assessed the nicotine dose-response relationship in intravenous self-administration (SA). β2Leu9'Ser rats self-administered nicotine doses 50 to 100 fold lower than the lowest doses that control rats would respond for. Expression of WT β2 subunits confirmed that this enhanced sensitivity to nicotine was due to the Leu9'Ser mutation in β2. Higher unit doses were associated with strong escalation in β2Leu9'Ser rats over 17 fixed ratio sessions. Escalation was minimal or absent in control rats at the same unit doses. In progressive ratio SA, β2Leu9'Ser rats exhibited higher breakpoints than control rats when the nicotine unit dose was 1.5 μg/kg/inf or higher. In intermittent access SA, β2Leu9'Ser rats exhibited response patterns very similar to control rats. By adding nicotine dose-response data, progressive ratio assays, and intermittent access results that rule out stereotypy, these data significantly extend our previous finding that nicotine activation of the mesolimbic dopamine pathway is sufficient for nicotine reinforcement.
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Affiliation(s)
- Noah B Walker
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Brenton R Tucker
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Leanne N Thomas
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Andrew E Tapp
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Dylan R Drenan
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Ryan M Drenan
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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Garcia-Rivas V, Fiancette JF, Tostain J, de Maio G, Ceau M, Wiart JF, Gaulier JM, Deroche-Gamonet V. Individual variations in motives for nicotine self-administration in male rats: evidence in support for a precision psychopharmacology. Transl Psychiatry 2024; 14:85. [PMID: 38336930 PMCID: PMC10858238 DOI: 10.1038/s41398-024-02774-6] [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: 11/30/2023] [Revised: 01/07/2024] [Accepted: 01/10/2024] [Indexed: 02/12/2024] Open
Abstract
The significant heterogeneity in smoking behavior among smokers, coupled with the inconsistent efficacy of approved smoking cessation therapies, supports the presence of individual variations in the mechanisms underlying smoking. This emphasizes the need to shift from standardized to personalized smoking cessation therapies. However, informed precision medicine demands precision fundamental research. Tobacco smoking is influenced and sustained by diverse psychopharmacological interactions between nicotine and environmental stimuli. In the classical experimental rodent model for studying tobacco dependence, namely intravenous self-administration of nicotine, seeking behavior is reinforced by the combined delivery of nicotine and a discrete cue (nicotine+cue). Whether self-administration behavior is driven by the same psychopharmacological mechanisms across individual rats remains unknown and unexplored. To address this, we employed behavioral pharmacology and unbiased cluster analysis to investigate individual differences in the mechanisms supporting classical intravenous nicotine self-administration (0.04 mg/kg/infusion) in male outbred Sprague-Dawley rats. Our analysis identified two clusters: one subset of rats sought nicotine primarily for its reinforcing effects, while the second subset sought nicotine to enhance the reinforcing effects of the discrete cue. Varenicline (1 mg/kg i.p.) reduced seeking behavior in the former group, whereas it tended to increase in the latter group. Crucially, despite this fundamental qualitative difference revealed by behavioral manipulation, the two clusters exhibited quantitatively identical nicotine+cue self-administration behavior. The traditional application of rodent models to study the reinforcing and addictive effects of nicotine may mask individual variability in the underlying motivational mechanisms. Accounting for this variability could significantly enhance the predictive validity of translational research.
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Affiliation(s)
- Vernon Garcia-Rivas
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France.
- INSERM, Magendie, U1215, F-33000, Bordeaux, France.
- Yale University School of Medicine, Department of Psychiatry, New Haven, CT, USA.
| | - Jean-François Fiancette
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France
- INSERM, Magendie, U1215, F-33000, Bordeaux, France
| | - Jessica Tostain
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France
- INSERM, Magendie, U1215, F-33000, Bordeaux, France
| | - Giulia de Maio
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France
- INSERM, Magendie, U1215, F-33000, Bordeaux, France
| | - Matias Ceau
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France
- INSERM, Magendie, U1215, F-33000, Bordeaux, France
| | | | - Jean-Michel Gaulier
- CHU Lille, Unité Fonctionnelle de Toxicologie, F-59037, Lille, France
- Univ. Lille, ULR 4483, IMPECS - IMPact de l'Environnement Chimique sur la Santé humaine, F-59045, Lille, France
| | - Véronique Deroche-Gamonet
- Univ. Bordeaux, INSERM, Magendie, U1215, F-33000, Bordeaux, France.
- INSERM, Magendie, U1215, F-33000, Bordeaux, France.
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Sved AF, Caggiula AR, Donny EC. Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri. Psychopharmacology (Berl) 2023; 240:417-430. [PMID: 36329195 PMCID: PMC11188050 DOI: 10.1007/s00213-022-06266-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.
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Affiliation(s)
- Alan F Sved
- Departments of Neuroscience, Psychiatry and Psychology and the Center for Neuroscience, University of Pittsburgh, 210 Langley Hall, Pittsburgh, PA, 15260, USA.
| | - Anthony R Caggiula
- Departments of Psychology and Psychiatry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Eric C Donny
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
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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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