1
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Vielle C. Beyond the Illusion of Controlled Environments: How to Embrace Ecological Pertinence in Research? Eur J Neurosci 2025; 61:e16661. [PMID: 39777969 DOI: 10.1111/ejn.16661] [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: 11/04/2024] [Revised: 12/11/2024] [Accepted: 12/16/2024] [Indexed: 01/11/2025]
Abstract
Through the lens of preclinical research on substance use disorders (SUD), I propose a reflection aimed at re-evaluating animal models in neuroscience, with a focus on ecological relevance. While rodent models have provided valuable insights into the neurobiology of SUD, the field currently faces a validation crisis, with findings often failing to translate into effective human treatments. Originally designed to address the lack of reproducibility in animal studies, the current global gold standard of rigorous standardization has led to increasingly controlled environments. This growing disconnection between laboratory settings and real-world scenarios exacerbates the validation crisis. Rodent models have also revealed various environmental influences on drug use and its neural mechanisms, highlighting parallels with human behaviour and underscoring the importance of ecological relevance in behavioural research. Drawing inspiration from inquiries in ethology and evolutionary biology, I advocate for incorporating greater environmental complexity into animal models. In line with this idea, the neuroethological approach involves studying spontaneous behaviours in seminatural habitats while utilizing advanced technologies to monitor neural activity. Although this framework offers new insights into human neuroscience, it does not adequately capture the complex human conditions that lead to neuropsychiatric diseases. Therefore, preclinical research should prioritize understanding the environmental factors that shape human behaviour and neural architecture, integrating these insights into animal models. By emphasizing ecological relevance, we can achieve deeper insights into neuropsychiatric disorders and develop more effective treatment strategies. This approach highlights significant benefits for both scientific inquiry and ethical considerations. The controlled environment is a chimera; it is time to rethink our models. Here, I have chosen the prism of preclinical research on SUD to present, in a nonexhaustive manner, advances enabled by the use of rodent models, the crises faced by animal experimentation, the reflections and responses provided by laboratories, to finally propose rethinking our models around questions of ecological relevance, in order to improve both ethics and scientific quality. Although my discussion is illustrated by the situation in preclinical research on SUD, the observation drawn from it and the proposals made can extend to many other domains and species.
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Affiliation(s)
- Cassandre Vielle
- Department of Biology, Concordia University, Montreal, QC, Canada
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2
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Lenoir M, Engeln M, Navailles S, Girardeau P, Ahmed SH. A large-scale c-Fos brain mapping study on extinction of cocaine-primed reinstatement. Neuropsychopharmacology 2024; 49:1459-1467. [PMID: 38664549 PMCID: PMC11251268 DOI: 10.1038/s41386-024-01867-6] [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: 01/12/2024] [Revised: 03/29/2024] [Accepted: 04/11/2024] [Indexed: 07/17/2024]
Abstract
Individuals with cocaine addiction can experience many craving episodes and subsequent relapses, which represents the main obstacle to recovery. Craving is often favored when abstinent individuals ingest a small dose of cocaine, encounter cues associated with drug use or are exposed to stressors. Using a cocaine-primed reinstatement model in rat, we recently showed that cocaine-conditioned interoceptive cues can be extinguished with repeated cocaine priming in the absence of drug reinforcement, a phenomenon we called extinction of cocaine priming. Here, we applied a large-scale c-Fos brain mapping approach following extinction of cocaine priming in male rats to identify brain regions implicated in processing the conditioned interoceptive stimuli of cocaine priming. We found that cocaine-primed reinstatement is associated with increased c-Fos expression in key brain regions (e.g., dorsal and ventral striatum, several prefrontal areas and insular cortex), while its extinction mostly disengages them. Moreover, while reinstatement behavior was correlated with insular and accumbal activation, extinction of cocaine priming implicated parts of the ventral pallidum, the mediodorsal thalamus and the median raphe. These brain patterns of activation and inhibition suggest that after repeated priming, interoceptive signals lose their conditioned discriminative properties and that action-outcome associations systems are mobilized in search for new contingencies, a brain state that may predispose to rapid relapse.
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Affiliation(s)
- Magalie Lenoir
- Univ. Bordeaux, CNRS, INCIA, UMR 5287, F-33000, Bordeaux, France.
| | - Michel Engeln
- Univ. Bordeaux, CNRS, INCIA, UMR 5287, F-33000, Bordeaux, France.
| | | | - Paul Girardeau
- Univ. Bordeaux, UFR des Sciences Odontologiques, Bordeaux, France
| | - Serge H Ahmed
- Univ. Bordeaux, CNRS, INCIA, UMR 5287, F-33000, Bordeaux, France
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3
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Beasley MM, Tunstall BJ, Kearns DN. Intermittent access cocaine self-administration produces context-specific escalation and increased motivation. Drug Alcohol Depend 2023; 245:109797. [PMID: 36801708 PMCID: PMC10033440 DOI: 10.1016/j.drugalcdep.2023.109797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/27/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023]
Abstract
The intermittent-access (IntA) self-administration procedure has been reported to produce intensified addiction-like behavior compared to continuous-access (ContA) procedures. In a common variation of the IntA procedure, cocaine is available for 5 min at the beginning of each half hour of a 6-h session. In contrast, during ContA procedures, cocaine is available continuously throughout a session, typically lasting one or more hours. Previous studies comparing procedures have used between-subjects designs, where separate groups of rats self-administer cocaine on either IntA or ContA procedures. The present study used a within-subjects design where subjects self-administered cocaine on the IntA procedure in one context and self-administered cocaine on the continuous short-access (ShA) procedure in another context during separate sessions. Across sessions, rats escalated cocaine intake in the IntA, but not ShA, context. Following sessions eight and 11, rats were administered a progressive ratio test in each context to monitor the change in cocaine motivation. Rats obtained more cocaine infusions on the progressive ratio test in the IntA context than in the ShA context following 11 sessions. These results suggest that addiction-like behaviors following IntA self-administration may be influenced by context-specific learning factors.
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Affiliation(s)
| | - Brendan J Tunstall
- Department of Pharmacology, Addiction Science, and Toxicology, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | - David N Kearns
- Psychology Department, American University, Washington, DC, USA
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4
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Lenoir M, Navailles S, Vandaele Y, Vouillac-Mendoza C, Guillem K, Ahmed SH. Large-scale brain correlates of sweet versus cocaine reward in rats. Eur J Neurosci 2023; 57:423-439. [PMID: 36453530 DOI: 10.1111/ejn.15879] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 11/09/2022] [Accepted: 11/20/2022] [Indexed: 12/03/2022]
Abstract
Cocaine induces many supranormal changes in neuronal activity in the brain, notably in learning- and reward-related regions, in comparison with nondrug rewards-a difference that is thought to contribute to its relatively high addictive potential. However, when facing a choice between cocaine and a nondrug reward (e.g., water sweetened with saccharin), most rats do not choose cocaine, as one would expect from the extent and magnitude of its global activation of the brain, but instead choose the nondrug option. We recently showed that cocaine, though larger in magnitude, is also an inherently more delayed reward than sweet water, thereby explaining why it has less value during choice and why rats opt for the more immediate nondrug option. Here, we used a large-scale Fos brain mapping approach to measure brain responses to each option in saccharin-preferring rats, with the hope to identify brain regions whose activity may explain the preference for the nondrug option. In total, Fos expression was measured in 142 brain levels corresponding to 52 brain subregions and composing 5 brain macrosystems. Overall, our findings confirm in rats with a preference for saccharin that cocaine induces more global brain activation than the preferred nondrug option does. Only very few brain regions were uniquely activated by saccharin. They included regions involved in taste processing (i.e., anterior gustatory cortex) and also regions involved in processing reward delay and intertemporal choice (i.e., some components of the septohippocampal system and its connections with the lateral habenula).
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Affiliation(s)
- Magalie Lenoir
- Université de Bordeaux, CNRS, INCIA, UMR 5287, Bordeaux, France
| | | | - Youna Vandaele
- INSERM, U-1084, Laboratoire des Neurosciences Expérimentales et Cliniques, Université de Poitiers, Poitiers, France
| | | | - Karine Guillem
- Université de Bordeaux, CNRS, INCIA, UMR 5287, Bordeaux, France
| | - Serge H Ahmed
- Université de Bordeaux, CNRS, INCIA, UMR 5287, Bordeaux, France
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5
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Padovan-Hernandez Y, Rojas G, Wu L, Knackstedt LA. Individual differences in cocaine seeking during voluntary abstinence predicts cocaine relapse and the circuitry mediating relapse. Psychopharmacology (Berl) 2022; 239:3963-3973. [PMID: 36329194 PMCID: PMC10240883 DOI: 10.1007/s00213-022-06270-x] [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: 04/18/2022] [Accepted: 10/24/2022] [Indexed: 11/06/2022]
Abstract
RATIONALE There are no FDA-approved treatments to facilitate recovery from cocaine use disorder. Contingency management offers non-drug reinforcers to encourage abstinence and is effective at reducing drug seeking during treatment, but once discontinued, relapse rates increase. OBJECTIVES We sought to establish a choice-based rodent model of voluntary abstinence (VA) from cocaine to test the ability of ceftriaxone, an antibiotic consistently shown to prevent relapse to cocaine seeking in rodents, to attenuate relapse after discontinuation of VA, and to investigate relapse-induced neuronal activation via c-Fos expression. METHODS Male Sprague-Dawley rats self-administered sucrose pellets for 5 days and intravenous cocaine for 12 days. Rats then underwent 14 days of voluntary or forced abstinence. VA sessions entailed the opportunity to choose between sucrose and cocaine delivery in discrete trials (20 trials/day). Ceftriaxone (or vehicle) was administered during the last 7 days of abstinence. During a relapse test, only the cocaine-paired lever was available and presses on the lever delivered cocaine-paired cues. RESULTS There were more presses on the sucrose lever during VA, but cocaine intake did not decline to zero. Ceftriaxone had no effect on cocaine intake during VA. Neither ceftriaxone nor VA reduced cocaine seeking during the relapse test, and cocaine intake during VA positively correlated with cocaine seeking during the test in vehicle-treated animals. Relapse-induced c-Fos expression was found to be greater in the ventral orbitofrontal cortex following VA. CONCLUSIONS Sucrose availability leads to a decrease in, but not cessation of, cocaine seeking and a differential engagement of the circuitry underlying relapse.
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Affiliation(s)
- Yasmin Padovan-Hernandez
- Psychology Department, University of Florida, 114 Psychology, 945 Center Dr, Gainesville, FL, 32611, USA
- Center for Addiction Research and Education, University of Florida, Gainesville, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, USA
| | - Giselle Rojas
- Psychology Department, University of Florida, 114 Psychology, 945 Center Dr, Gainesville, FL, 32611, USA
| | - Lizhen Wu
- Psychology Department, University of Florida, 114 Psychology, 945 Center Dr, Gainesville, FL, 32611, USA
| | - Lori A Knackstedt
- Psychology Department, University of Florida, 114 Psychology, 945 Center Dr, Gainesville, FL, 32611, USA.
- Center for Addiction Research and Education, University of Florida, Gainesville, USA.
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6
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Kelly AL, Baugh ME, Oster ME, DiFeliceantonio AG. The impact of caloric availability on eating behavior and ultra-processed food reward. Appetite 2022; 178:106274. [PMID: 35963586 PMCID: PMC9749763 DOI: 10.1016/j.appet.2022.106274] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 07/07/2022] [Accepted: 08/07/2022] [Indexed: 12/19/2022]
Abstract
The food environment has changed rapidly and dramatically in the last 50 years. While industrial food processing has increased the safety and stability of the food supply, a rapid expansion in the scope and scale of food processing in the 1980's has resulted in a market dominated by ultra-processed foods. Here, we use the NOVA definition of category 4 ultra-processed foods (UPFs) as they make up around 58% of total calories consumed in the US and 66% of calories in US children. UPFs are formulated from ingredients with no or infrequent culinary use, contain additives, and have a long shelf-life, spending long periods in contact with packaging materials, allowing for the absorption of compounds from those materials. The full implications of this dietary shift to UPFs on human health and disease outcomes are difficult, if not impossible, to quantify. However, UPF consumption is linked with various forms of cancer, increased cardiovascular disease, and increased all-cause mortality. Understanding food choice is, therefore, a critical problem in health research. Although many factors influence food choice, here we focus on the properties of the foods themselves. UPFs are generally treated as food, not as the highly refined, industrialized substances that they are, whose properties and components must be studied. Here, we examine one property of UPFs, that they deliver useable calories rapidly as a potential factor driving UPF overconsumption. First, we explore evidence that UPFs deliver calories more rapidly. Next, we examine the role of the gut-brain axis and its interplay with canonical reward systems, and last, we describe how speed affects both basic learning processes and drugs of abuse.
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Affiliation(s)
- Amber L Kelly
- Fralin Biomedical Research Institute at Virginia Tech Carilion, USA
| | | | - Mary E Oster
- Fralin Biomedical Research Institute at Virginia Tech Carilion, USA
| | - Alexandra G DiFeliceantonio
- Fralin Biomedical Research Institute at Virginia Tech Carilion, USA; Center for Health Behaviors Research; Department of Human Nutrition Foods and Exercise at Virginia Tech, USA.
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7
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Vanderschuren LJMJ, Ahmed SH. Animal Models of the Behavioral Symptoms of Substance Use Disorders. Cold Spring Harb Perspect Med 2021; 11:cshperspect.a040287. [PMID: 32513674 PMCID: PMC8327824 DOI: 10.1101/cshperspect.a040287] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
To more effectively manage substance use disorders, it is imperative to understand the neural, genetic, and psychological underpinnings of addictive behavior. To contribute to this understanding, considerable efforts have been made to develop translational animal models that capture key behavioral characteristics of addiction on the basis of DSM5 criteria of substance use disorders. In this review, we summarize empirical evidence for the occurrence of addiction-like behavior in animals. These symptoms include escalation of drug use, neurocognitive deficits, resistance to extinction, exaggerated motivation for drugs, increased reinstatement of drug seeking after extinction, preference for drugs over nondrug rewards, and resistance to punishment. The occurrence of addiction-like behavior in laboratory animals has opened the opportunity to investigate the neural, genetic, and psychological background of key aspects of addiction, which may ultimately contribute to the prevention and treatment of substance use disorders.
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Affiliation(s)
- Louk J M J Vanderschuren
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, 3584 CM Utrecht, the Netherlands
| | - Serge H Ahmed
- Université de Bordeaux, Bordeaux Neurocampus, Institut des Maladies Neurodégénératives, CNRS UMR 5293, F-33000 Bordeaux, France
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8
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Canchy L, Girardeau P, Durand A, Vouillac-Mendoza C, Ahmed SH. Pharmacokinetics trumps pharmacodynamics during cocaine choice: a reconciliation with the dopamine hypothesis of addiction. Neuropsychopharmacology 2021; 46:288-296. [PMID: 32731253 PMCID: PMC7853096 DOI: 10.1038/s41386-020-0786-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/10/2020] [Accepted: 07/24/2020] [Indexed: 01/08/2023]
Abstract
Cocaine is known to increase brain dopamine at supranormal levels in comparison to alternative nondrug rewards. According to the dopamine hypothesis of addiction, this abnormally large dopamine response would explain why cocaine use is initially highly rewarding and addictive. Though resting on solid neuroscientific foundations, this hypothesis has nevertheless proven difficult to reconcile with research on cocaine choice in experimental animals. When facing a choice between an intravenous bolus of cocaine and a nondrug alternative (e.g., sweet water), both delivered immediately after choice, rats do not choose the drug, as would be predicted, but instead develop a strong preference for the nondrug alternative. Here we report evidence that reconciles this finding with the dopamine hypothesis of addiction. First, a systematic literature analysis revealed that the delays of effects of intravenous cocaine on nucleus accumbens dopamine are of the order of tens of seconds and are considerably longer than those of nondrug reward. Second, this was confirmed by measuring response times to cocaine omission during self-administration as a behavioral proxy of these delays. Finally, when the influence of the drug delays was reduced during choice by adding an increasing delay to both the drug and nondrug rewards, rats shifted their choice to cocaine. Overall, this study suggests that cocaine is indeed supranormal in reward magnitude, as postulated by the dopamine hypothesis of addiction, but is less preferred during choice because its pharmacokinetics makes it an inherently more delayed reward than the alternative. Reframing previous drug choice studies in rats as intertemporal choice studies reveals that the discounting effects of delays spare no rewards, including supranormal ones, and that during choice, pharmacokinetics trumps pharmacodynamics.
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Affiliation(s)
- Ludivine Canchy
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France
- CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France
| | - Paul Girardeau
- Université de Bordeaux, UFR des Sciences Odontologiques, 146 rue Léo-Saignat, F-33000, Bordeaux, France
| | - Audrey Durand
- Imetronic®, 156 avenue Jean Jaurès, F-33600, Pessac, France
| | - Caroline Vouillac-Mendoza
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France
- CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France
| | - Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France.
- CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000, Bordeaux, France.
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9
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Improving translation of animal models of addiction and relapse by reverse translation. Nat Rev Neurosci 2020; 21:625-643. [PMID: 33024318 DOI: 10.1038/s41583-020-0378-z] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2020] [Indexed: 12/13/2022]
Abstract
Critical features of human addiction are increasingly being incorporated into complementary animal models, including escalation of drug intake, punished drug seeking and taking, intermittent drug access, choice between drug and non-drug rewards, and assessment of individual differences based on criteria in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Combined with new technologies, these models advanced our understanding of brain mechanisms of drug self-administration and relapse, but these mechanistic gains have not led to improvements in addiction treatment. This problem is not unique to addiction neuroscience, but it is an increasing source of disappointment and calls to regroup. Here we first summarize behavioural and neurobiological results from the animal models mentioned above. We then propose a reverse translational approach, whose goal is to develop models that mimic successful treatments: opioid agonist maintenance, contingency management and the community-reinforcement approach. These reverse-translated 'treatments' may provide an ecologically relevant platform from which to discover new circuits, test new medications and improve translation.
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10
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Kearns DN, Silberberg A. Opening the cocaine economy by providing within-session access to a cheaper source of cocaine makes demand for it more elastic. Behav Pharmacol 2020; 31:448-457. [PMID: 31625978 PMCID: PMC7182474 DOI: 10.1097/fbp.0000000000000510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies found that opening the cocaine economy by providing postsession access to cocaine had no effect on animals' demand for cocaine, whereas postsession access to saccharin or food made demand for these nondrug reinforcers more elastic. It is possible that there was no effect of economy type on cocaine taking in these earlier studies because of the delay to the postsession cocaine in the open economy. The present experiment tested whether forming an open economy by providing additional within-session cocaine, rather than postsession cocaine, would make rats' demand for cocaine more elastic. Saccharin was used as a nondrug comparison reinforcer. Three groups of rats pressed one lever for cocaine and one for saccharin on an ascending series of fixed ratio (FR) schedules where the number of responses required per reinforcer increased from 1 to 48 over sessions. In the open cocaine and open saccharin economy groups, rats had occasional access during the session to a third lever where cocaine or saccharin reinforcers, respectively, were always available on an FR-1 schedule. The main finding was that demand for cocaine was more elastic in the open cocaine economy group than in either of the other groups. Demand for saccharin was more elastic in the open saccharin economy group than in the open cocaine economy group. This study shows that cocaine taking is sensitive to economy type when the additional source of cocaine in an open economy is available close in time to when rats work for cocaine.
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Affiliation(s)
- David N Kearns
- Psychology Department, American University, Washington DC, USA
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11
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Ahmed SH, Badiani A, Miczek KA, Müller CP. Non-pharmacological factors that determine drug use and addiction. Neurosci Biobehav Rev 2020; 110:3-27. [PMID: 30179633 PMCID: PMC6395570 DOI: 10.1016/j.neubiorev.2018.08.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/26/2018] [Accepted: 08/28/2018] [Indexed: 12/26/2022]
Abstract
Based on their pharmacological properties, psychoactive drugs are supposed to take control of the natural reward system to finally drive compulsory drug seeking and consumption. However, psychoactive drugs are not used in an arbitrary way as pure pharmacological reinforcement would suggest, but rather in a highly specific manner depending on non-pharmacological factors. While pharmacological effects of psychoactive drugs are well studied, neurobiological mechanisms of non-pharmacological factors are less well understood. Here we review the emerging neurobiological mechanisms beyond pharmacological reinforcement which determine drug effects and use frequency. Important progress was made on the understanding of how the character of an environment and social stress determine drug self-administration. This is expanded by new evidence on how behavioral alternatives and opportunities for drug instrumentalization generate different patterns of drug choice. Emerging evidence suggests that the neurobiology of non-pharmacological factors strongly determines pharmacological and behavioral drug action and may, thus, give rise for an expanded system's approach of psychoactive drug use and addiction.
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Affiliation(s)
- Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - Aldo Badiani
- Department of Physiology and Pharmacology, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; Sussex Addiction Research and Intervention Centre (SARIC), School of Psychology, University of Sussex, BN1 9RH Brighton, UK
| | - Klaus A Miczek
- Psychology Department, Tufts University, Bacon Hall, 530 Boston Avenue, Medford, MA 02155, USA; Department of Neuroscience, Sackler School of Graduate Biomedical Sciences, Boston, MA 02111, USA
| | - Christian P Müller
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany.
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12
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Kuhn BN, Kalivas PW, Bobadilla AC. Understanding Addiction Using Animal Models. Front Behav Neurosci 2019; 13:262. [PMID: 31849622 PMCID: PMC6895146 DOI: 10.3389/fnbeh.2019.00262] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/15/2019] [Indexed: 12/13/2022] Open
Abstract
Drug addiction is a neuropsychiatric disorder with grave personal consequences that has an extraordinary global economic impact. Despite decades of research, the options available to treat addiction are often ineffective because our rudimentary understanding of drug-induced pathology in brain circuits and synaptic physiology inhibits the rational design of successful therapies. This understanding will arise first from animal models of addiction where experimentation at the level of circuits and molecular biology is possible. We will review the most common preclinical models of addictive behavior and discuss the advantages and disadvantages of each. This includes non-contingent models in which animals are passively exposed to rewarding substances, as well as widely used contingent models such as drug self-administration and relapse. For the latter, we elaborate on the different ways of mimicking craving and relapse, which include using acute stress, drug administration or exposure to cues and contexts previously paired with drug self-administration. We further describe paradigms where drug-taking is challenged by alternative rewards, such as appetitive foods or social interaction. In an attempt to better model the individual vulnerability to drug abuse that characterizes human addiction, the field has also established preclinical paradigms in which drug-induced behaviors are ranked by various criteria of drug use in the presence of negative consequences. Separation of more vulnerable animals according to these criteria, along with other innate predispositions including goal- or sign-tracking, sensation-seeking behavior or impulsivity, has established individual genetic susceptibilities to developing drug addiction and relapse vulnerability. We further examine current models of behavioral addictions such as gambling, a disorder included in the DSM-5, and exercise, mentioned in the DSM-5 but not included yet due to insufficient peer-reviewed evidence. Finally, after reviewing the face validity of the aforementioned models, we consider the most common standardized tests used by pharmaceutical companies to assess the addictive potential of a drug during clinical trials.
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Affiliation(s)
| | - Peter W. Kalivas
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
| | - Ana-Clara Bobadilla
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
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13
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Guillem K, Ahmed SH. Preference for Cocaine is Represented in the Orbitofrontal Cortex by an Increased Proportion of Cocaine Use-Coding Neurons. Cereb Cortex 2019; 28:819-832. [PMID: 28057724 DOI: 10.1093/cercor/bhw398] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 12/13/2016] [Indexed: 11/13/2022] Open
Abstract
Cocaine addiction is a harmful preference for drug use over and at the expense of other nondrug-related activities. Here we identify in the rat orbitofrontal cortex (OFC) a mechanism that explains individual preferences between cocaine use and an alternative, nondrug action. OFC neuronal activity was recorded while rats performed each of these 2 actions separately or while they chose between them. First, we found that these actions are encoded by 2 nonoverlapping neuronal populations and that the relative size of the cocaine population represented individual preferences. A larger relative size was only observed in cocaine-preferring individuals. Second, OFC neurons encoding a given individual's preferred action progressively fired more than other action-coding neurons few seconds before the preferred action was actually chosen, suggesting a prechoice neuronal competition for action selection. In cocaine-preferring rats, this manifested by a prechoice ramping-up activity in favor of the cocaine population. Finally, pharmacological manipulation of prechoice activity in favor of the cocaine population caused nondrug-preferring rats to shift their choice to cocaine. Overall, this study suggests that an individual preference for cocaine is represented in the OFC by a population size bias that systematically advantages cocaine use-coding neurons during prechoice competition for action selection.
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Affiliation(s)
- Karine Guillem
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France.,CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France.,CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
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14
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Inflexible habitual decision-making during choice between cocaine and a nondrug alternative. Transl Psychiatry 2019; 9:109. [PMID: 30842406 PMCID: PMC6403316 DOI: 10.1038/s41398-019-0445-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 02/12/2019] [Accepted: 02/16/2019] [Indexed: 11/09/2022] Open
Abstract
The concept of compulsive cocaine-seeking habits is difficult to reconcile with other evidence showing that humans and even rats remain able to shift their choice away from the drug and toward an alternative nondrug reward, when available. This paradox could dissolve if preference for the nondrug option reflected in fact inflexible habitual decision-making (i.e., fixed in a habitual control mode, with no return to a goal-directed control mode). Previous research in rats has shown that prior drug use can favor habit formation, but whether the resulting habits are inflexible or not is largely unknown. Here we addressed this question by manipulating the value of water in rats that chose between water and cocaine in a discrete-trials procedure. Rats preferred water when thirsty and maintained this preference despite water devaluation by satiation. Only with repeated daily testing under water satiation did they progressively reverse their preference toward cocaine. Additional evidence showed that this progressive reversal of preference reflected in fact new interoceptive discrimination learning. Overall, this study suggests that rats seem to be stuck in a habitual decision-making mode, unable to return to a goal-directed mode upon experiencing a change in options value. It also reveals that inflexible decision-making does not necessarily promote drug choice, but can also under some circumstances favor abstinence.
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15
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Farrell MR, Schoch H, Mahler SV. Modeling cocaine relapse in rodents: Behavioral considerations and circuit mechanisms. Prog Neuropsychopharmacol Biol Psychiatry 2018; 87:33-47. [PMID: 29305936 PMCID: PMC6034989 DOI: 10.1016/j.pnpbp.2018.01.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/18/2017] [Accepted: 01/02/2018] [Indexed: 12/29/2022]
Abstract
Addiction is a chronic relapsing disorder, in that most addicted individuals who choose to quit taking drugs fail to maintain abstinence in the long-term. Relapse is especially likely when recovering addicts encounter risk factors like small "priming" doses of drug, stress, or drug-associated cues and locations. In rodents, these same factors reinstate cocaine seeking after a period of abstinence, and extensive preclinical work has used priming, stress, or cue reinstatement models to uncover brain circuits underlying cocaine reinstatement. Here, we review common rat models of cocaine relapse, and discuss how specific features of each model influence the neural circuits recruited during reinstated drug seeking. To illustrate this point, we highlight the surprisingly specific roles played by ventral pallidum subcircuits in cocaine seeking reinstated by either cocaine-associated cues, or cocaine itself. One goal of such studies is to identify, and eventually to reverse the specific circuit activity that underlies the inability of some humans to control their drug use. Based on preclinical findings, we posit that circuit activity in humans also differs based on the triggers that precipitate craving and relapse, and that associated neural responses could help predict the triggers most likely to elicit relapse in a given person. If so, examining circuit activity could facilitate diagnosis of subgroups of addicted people, allowing individualized treatment based on the most problematic risk factors.
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Affiliation(s)
- Mitchell R Farrell
- Department of Neurobiology & Behavior, University of California, 1203 McGaugh Hall, Irvine, United States
| | - Hannah Schoch
- Department of Neurobiology & Behavior, University of California, 1203 McGaugh Hall, Irvine, United States
| | - Stephen V Mahler
- Department of Neurobiology & Behavior, University of California, 1203 McGaugh Hall, Irvine, United States.
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16
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Ahmed SH. Trying to make sense of rodents' drug choice behavior. Prog Neuropsychopharmacol Biol Psychiatry 2018; 87:3-10. [PMID: 28965843 DOI: 10.1016/j.pnpbp.2017.09.027] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 09/22/2017] [Accepted: 09/26/2017] [Indexed: 12/14/2022]
Abstract
Since the first experimental hint for the existence of "an actual desire or striving for the drug" in nonhuman animals by Sidney Spragg in the late 1930s, much effort has been expended by lab researchers to try to model in a valid manner the key behavioral aspects and signs of addiction in animals, typically in rodents (i.e., mainly rats and, to a lesser extent, mice). Despite much advances, there still remains a lingering doubt about the disordered status of drug use in rodents. This is mainly because drug use occurs in a particular setting where animals have access to a drug for self-administration but without access to other valuable behavioral options that could compete with and divert from drug use. Here I review evidence showing that enriching the drug setting with other behavioral options can dramatically influence the pattern of drug choices in rodents. Overall, access to other options during drug access can divert the vast majority of rats from continued drug use. Only few individuals continue to engage in drug use despite access to and at the expense of other options. However, there exist certain high-risk settings in which virtually all animals are vulnerable to develop a harmful pattern of exclusive drug use that can even become fatal in the long run if not discontinued by an outside intervention. Paradoxically, it appears that the behavioral trait that is hypothesized to uniquely render rodents vulnerable to the latter settings (i.e., a narrow focus on the local, current choice, with no consideration of the global pattern of choice) would also protect most of them from using drugs in other choice settings. I conclude with an attempt to make sense of this peculiar setting-specific behavior and with some general propositions for future research.
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Affiliation(s)
- Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France.
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17
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Freese L, Durand A, Guillem K, Ahmed SH. Pre-trial cocaine biases choice toward cocaine through suppression of the nondrug option. Pharmacol Biochem Behav 2018; 173:65-73. [PMID: 30056175 DOI: 10.1016/j.pbb.2018.07.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/25/2018] [Accepted: 07/26/2018] [Indexed: 12/17/2022]
Abstract
Being under the influence during choice between drug and nondrug options can have a dramatic effect on choice outcomes. When rats face a choice between cocaine and sweet water and are not under the influence, they prefer sweet water. In contrast, when they are under the influence of cocaine, this causes them to shift their choice to cocaine nearly exclusively. Here we sought to characterize the behavioral mechanisms underlying the influence of cocaine on choice. In theory, rats under the influence of cocaine should be in a mixed motivational state, at least temporarily, with both their motivation for cocaine and their motivation for the nondrug option suppressed by the drug satiating and anorexic effects of cocaine, respectively. For this mixed state to shift choice to cocaine, the satiated motivation for cocaine should recover before the suppressed motivation for the preferred nondrug option. The goal of the present study was to test this prediction in rats that expressed a preference for sweet water after extended access to cocaine self-administration. We measured their choice and response latencies to each option after pre-trial, passive administration of cocaine to estimate the duration of its drug satiating and anorexic effects. As expected, pre-trial cocaine caused most rats to shift their choice to cocaine. Though this shift was not simply due to a longer latency to respond for sweet water than for cocaine after pre-trial cocaine, it nevertheless occurred while rats' motivation for the nondrug option was still partially suppressed. Thus, cocaine seems to bias choice toward more cocaine mainly via suppression of the nondrug option.
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Affiliation(s)
- Luana Freese
- Laboratory of Neuropsychopharmacology, Federal University of Health Sciences of Porto Alegre (UFCSPA), Porto Alegre, Rio Grande do Sul, Brazil
| | - Audrey Durand
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - Karine Guillem
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France
| | - Serge H Ahmed
- Université de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 146 rue Léo-Saignat, F-33000 Bordeaux, France.
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18
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Guillem K, Brenot V, Durand A, Ahmed SH. Neuronal representation of individual heroin choices in the orbitofrontal cortex. Addict Biol 2018; 23:880-888. [PMID: 28703355 DOI: 10.1111/adb.12536] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/12/2017] [Accepted: 06/21/2017] [Indexed: 02/06/2023]
Abstract
Drug addiction is a harmful preference for drug use over and at the expense of other non-drug-related activities. We previously identified in the rat orbitofrontal cortex (OFC) a mechanism that influences individual preferences between cocaine use and an alternative action rewarded by a non-drug reward (i.e. sweet water). Here, we sought to test the generality of this mechanism to a different addictive drug, heroin. OFC neuronal activity was recorded while rats responded for heroin or the alternative non-drug reward separately or while they chose between the two. First, we found that heroin-rewarded and sweet water-rewarded actions were encoded by two non-overlapping OFC neuronal populations and that the relative size of the heroin population represented individual drug choices. Second, OFC neurons encoding the preferred action-which was the non-drug action in the large majority of individuals-progressively fired more than non-preferred action-coding neurons 1 second after the onset of choice trials and around 1 second before the preferred action was actually chosen, suggesting a pre-choice neuronal competition for action selection. Together with a previous study on cocaine choice, the present study on heroin choice reveals important commonalities in how OFC neurons encode individual drug choices and preferences across different classes of drugs. It also reveals some drug-specific differences in OFC encoding activity. Notably, the proportion of neurons that non-selectively encode both the drug and the non-drug reward was higher when the drug was heroin (present study) than when it was cocaine (previous study). We will discuss the potential functional significance of these commonalities and differences in OFC neuronal activity across different drugs for understanding drug choice.
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Affiliation(s)
- Karine Guillem
- Université de Bordeaux; Institut des Maladies Neurodégénératives; France
- CNRS; Institut des Maladies Neurodégénératives; France
| | - Viridiana Brenot
- Université de Bordeaux; Institut des Maladies Neurodégénératives; France
| | - Audrey Durand
- Université de Bordeaux; Institut des Maladies Neurodégénératives; France
- CNRS; Institut des Maladies Neurodégénératives; France
| | - Serge H. Ahmed
- Université de Bordeaux; Institut des Maladies Neurodégénératives; France
- CNRS; Institut des Maladies Neurodégénératives; France
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Parrilla-Carrero J, Buchta WC, Goswamee P, Culver O, McKendrick G, Harlan B, Moutal A, Penrod R, Lauer A, Ramakrishnan V, Khanna R, Kalivas P, Riegel AC. Restoration of Kv7 Channel-Mediated Inhibition Reduces Cued-Reinstatement of Cocaine Seeking. J Neurosci 2018; 38:4212-4229. [PMID: 29636392 PMCID: PMC5963852 DOI: 10.1523/jneurosci.2767-17.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 03/27/2018] [Accepted: 03/29/2018] [Indexed: 12/16/2022] Open
Abstract
Cocaine addicts display increased sensitivity to drug-associated cues, due in part to changes in the prelimbic prefrontal cortex (PL-PFC). The cellular mechanisms underlying cue-induced reinstatement of cocaine seeking remain unknown. Reinforcement learning for addictive drugs may produce persistent maladaptations in intrinsic excitability within sparse subsets of PFC pyramidal neurons. Using a model of relapse in male rats, we sampled >600 neurons to examine spike frequency adaptation (SFA) and afterhyperpolarizations (AHPs), two systems that attenuate low-frequency inputs to regulate neuronal synchronization. We observed that training to self-administer cocaine or nondrug (sucrose) reinforcers decreased SFA and AHPs in a subpopulation of PL-PFC neurons. Only with cocaine did the resulting hyperexcitability persist through extinction training and increase during reinstatement. In neurons with intact SFA, dopamine enhanced excitability by inhibiting Kv7 potassium channels that mediate SFA. However, dopamine effects were occluded in neurons from cocaine-experienced rats, where SFA and AHPs were reduced. Pharmacological stabilization of Kv7 channels with retigabine restored SFA and Kv7 channel function in neuroadapted cells. When microinjected bilaterally into the PL-PFC 10 min before reinstatement testing, retigabine reduced cue-induced reinstatement of cocaine seeking. Last, using cFos-GFP transgenic rats, we found that the loss of SFA correlated with the expression of cFos-GFP following both extinction and re-exposure to drug-associated cues. Together, these data suggest that cocaine self-administration desensitizes inhibitory Kv7 channels in a subpopulation of PL-PFC neurons. This subpopulation of neurons may represent a persistent neural ensemble responsible for driving drug seeking in response to cues.SIGNIFICANCE STATEMENT Long after the cessation of drug use, cues associated with cocaine still elicit drug-seeking behavior, in part by activation of the prelimbic prefrontal cortex (PL-PFC). The underlying cellular mechanisms governing these activated neurons remain unclear. Using a rat model of relapse to cocaine seeking, we identified a population of PL-PFC neurons that become hyperexcitable following chronic cocaine self-administration. These neurons show persistent loss of spike frequency adaptation, reduced afterhyperpolarizations, decreased sensitivity to dopamine, and reduced Kv7 channel-mediated inhibition. Stabilization of Kv7 channel function with retigabine normalized neuronal excitability, restored Kv7 channel currents, and reduced drug-seeking behavior when administered into the PL-PFC before reinstatement. These data highlight a persistent adaptation in a subset of PL-PFC neurons that may contribute to relapse vulnerability.
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Affiliation(s)
- Jeffrey Parrilla-Carrero
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - William C Buchta
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Priyodarshan Goswamee
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Oliver Culver
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Greer McKendrick
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Benjamin Harlan
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Aubin Moutal
- Department of Pharmacology, University of Arizona, Tucson, Arizona 85724, and
| | - Rachel Penrod
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Abigail Lauer
- Department of Public Health Sciences., Medical University of South Carolina, Charleston, SC 29425
| | - Viswanathan Ramakrishnan
- Department of Public Health Sciences., Medical University of South Carolina, Charleston, SC 29425
| | - Rajesh Khanna
- Department of Pharmacology, University of Arizona, Tucson, Arizona 85724, and
| | - Peter Kalivas
- Department of Neuroscience
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Arthur C Riegel
- Department of Neuroscience,
- Neurobiology of Addiction Research Center, Medical University of South Carolina, Charleston, South Carolina 29425
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20
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Social Stress-Induced Alterations in CRF Signaling in the VTA Facilitate the Emergence of Addiction-like Behavior. J Neurosci 2018; 36:8780-2. [PMID: 27559161 DOI: 10.1523/jneurosci.1815-16.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/19/2016] [Indexed: 11/21/2022] Open
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21
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Ginsburg BC, Lamb RJ. Frustration stress (unexpected loss of alternative reinforcement) increases opioid self-administration in a model of recovery. Drug Alcohol Depend 2018; 182:33-39. [PMID: 29136564 DOI: 10.1016/j.drugalcdep.2017.09.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/13/2017] [Accepted: 09/14/2017] [Indexed: 12/23/2022]
Abstract
PURPOSE Engaging in alternative activities in the context where opioid use had occurred can constrain opioid use and helps to maintain recovery. However, "frustration stress" that occurs when contingencies on these alternative activities unexpectedly change (e.g., job loss or divorce) is thought to threaten recovery by prompting a return to drug use. Yet it remains unclear whether frustration stress can result in a return to drug use, and if so, whether it returns to prior levels or to even greater levels. PROCEDURES We examine the impact of unsignaled extinction of alternative reinforcement on opioid use. Rats were trained to respond for an etonitazene solution (5μg/ml, p.o.), then for food in alternating daily sessions. Subsequently, food and etonitazene were made concurrently available. Under concurrent availability conditions, rats were exposed to 1, 2, or 4 sessions of unsignaled food extinction, and effects on responding for etonitazene and food measured. FINDINGS When etonitazene was the only reinforcer available, rats earned 58.3±20.3μg/kg/session (mean±S.E.M.). When food was available in alternating sessions, etonitazene earned was unchanged (65.3±19.2μg/kg/session). Concurrent food availability decreased etonitazene earned (13.5±4.5μg/kg/session). Unsignaled food extinction returned etonitazene earnedto levels similar to (60.5±18.4μg/kg/session), but not greater than, those observed previously when etonitazene alone was available. CONCLUSIONS Unsignaled extinction of alternative behavior controlling opioid use can result in increased opioid use, but this use does not rise beyond previous levels observed when opioid use is unconstrained by alternative reinforced behavior.
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Affiliation(s)
- Brett C Ginsburg
- Department of Psychiatry, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
| | - R J Lamb
- Department of Psychiatry, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA; Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
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22
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Kearns DN, Kim JS, Tunstall BJ, Silberberg A. Essential values of cocaine and non-drug alternatives predict the choice between them. Addict Biol 2017; 22:1501-1514. [PMID: 27623729 DOI: 10.1111/adb.12450] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 07/26/2016] [Accepted: 08/14/2016] [Indexed: 02/04/2023]
Abstract
This study investigated the relationship between reinforcer value and choice between cocaine and two non-drug alternative reinforcers in rats. The essential value (EV, a behavioral economic measure based on elasticity of demand) of intravenous cocaine and food (Experiment 1) or saccharin (Experiment 2) was determined in the first phase of each experiment. Food had higher EV than cocaine, whereas the EVs of cocaine and saccharin did not differ. In the second phase of each experiment, rats were allowed to make mutually exclusive choices between cocaine and the non-drug alternative reinforcer. The main findings were that the EV of cocaine was a positive predictor of cocaine preference and the EV of food or saccharin was a negative predictor of cocaine preference. An analysis of within-session patterns of choice behavior revealed sequential dependencies, whereby rats were more likely to choose cocaine on a particular trial after having chosen the non-drug alternative on previous trials. When the time between choices was increased, these sequential dependencies disappeared. The results of these experiments are consistent with the suggestion that addiction-like behavior involves both overvaluation of drug reinforcers and undervaluation of non-drug reinforcers.
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Affiliation(s)
- David N. Kearns
- Psychology Department; American University; Washington DC USA
| | - Jung S. Kim
- Psychology Department; American University; Washington DC USA
| | - Brendan J. Tunstall
- Intramural Research Program; National Institute on Drug Abuse; Baltimore MD USA
| | - Alan Silberberg
- Psychology Department; American University; Washington DC USA
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23
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Abstract
BACKGROUND Several recent studies have investigated the choice between heroin and a non-drug alternative reinforcer in rats. A common finding in these studies is that there are large individual differences in preference, with some rats preferring heroin and some preferring the non-drug alternative. The primary goal of the present study was to determine whether individual differences in how heroin or saccharin is valued, based on demand analysis, predicts choice. METHODS Rats lever-pressed for heroin infusions and saccharin reinforcers on fixed-ratio schedules. The essential value of each reinforcer was obtained from resulting demand curves. Rats were then trained on a mutually exclusive choice procedure where pressing one lever resulted in heroin and pressing another resulted in saccharin. After seven sessions of increased access to heroin or saccharin, rats were reexposed to the demand and choice procedures. RESULTS Demand for heroin was more elastic than demand for saccharin (i.e., heroin had lower essential value than saccharin). When allowed to choose, most rats preferred saccharin. The essential value of heroin, but not saccharin, predicted preference. The essential value of both heroin and saccharin increased following a week of increased access to heroin, but similar saccharin exposure had no effect on essential value. Preference was unchanged after increased access to either reinforcer. CONCLUSION Heroin-preferring rats differed from saccharin-preferring rats in how they valued heroin, but not saccharin. To the extent that choice models addiction-related behavior, these results suggest that overvaluation of opioids specifically, rather than undervaluation of non-drug alternatives, could identify susceptible individuals.
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Affiliation(s)
| | - Jung S. Kim
- Psychology Department, American University, Washington, DC
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Tunstall BJ, Kearns DN. Cocaine can generate a stronger conditioned reinforcer than food despite being a weaker primary reinforcer. Addict Biol 2016; 21:282-93. [PMID: 25363637 DOI: 10.1111/adb.12195] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The present study aimed to test the hypothesis that cues associated with drug-taking behavior become extra strong motivators of behavior compared with cues paired with non-drug reinforcers. In experiment 1, rats were trained to lever press for intravenous cocaine infusions and grain pellets. Each reinforcer was paired with a distinct audiovisual cue. When allowed to choose between these alternatives, rats chose grain on ~70-80 percent of trials. However, after extinguishing lever pressing, reintroduction of press-contingent cues during a test for cue-induced reinstatement generated more cocaine seeking than grain seeking (also observed on 3- and 8-week follow-up tests). To examine whether the same pattern of results would occur with two non-drug reinforcers, experiment 2 replicated experiment 1 using grain and sucrose as reinforcement alternatives. Rats chose sucrose over grain on ~70-80 percent of choice trials and also responded more for the sucrose cue than for the grain cue on the reinstatement test. The disconnect between primary and conditioned reinforcements in experiment 1 but not in experiment 2 suggests that drug cues may become exceptionally strong motivators of drug seeking. These results are consistent with cue-focused theories of addiction and may offer insight into the persistent cue-driven drug-seeking behavior observed in addiction.
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Affiliation(s)
| | - David N. Kearns
- Psychology Department; American University; Washington DC USA
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25
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Choosing Under the Influence: A Drug-Specific Mechanism by Which the Setting Controls Drug Choices in Rats. Neuropsychopharmacology 2016; 41:646-57. [PMID: 26129679 PMCID: PMC5130140 DOI: 10.1038/npp.2015.195] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 06/22/2015] [Accepted: 06/24/2015] [Indexed: 02/05/2023]
Abstract
Ample evidence shows that the setting can control drug choices in both humans and animals. Here we reveal in rats that a major mechanism of this control involves a regulation of the drug influence on other competing options at the time of choice. Briefly, rats were offered a choice between a drug dose (cocaine or heroin) and a brief access to water sweetened with saccharin in two different settings. In one setting, choosing under the influence was not possible and rats largely preferred saccharin over either cocaine or heroin. In contrast, when the same rats were shifted to a setting where choosing under the influence was possible, they chose the drug either nonexclusively or exclusively depending on whether the drug enhanced or suppressed sweet reward, respectively. Thus, when rats were under the orexigenic influence of heroin at the time of choice, they more frequently chose saccharin in alternation with heroin. In contrast, when rats were under the anorexic influence of cocaine, they stopped choosing saccharin and continued taking cocaine exclusively. These setting- and drug-specific changes in preference were rapid and reversible, and could be induced by passively administering cocaine or heroin before choice. Finally, rats behaved as if they were oblivious to the drug influence on their choices. This behavior could explain why rats are vulnerable to harm themselves, sometimes to the point of death, in settings where choices are made under the drug influence, notably if this influence excludes other important options or, conversely, enhances harmful ones.
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26
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Caprioli D, Zeric T, Thorndike EB, Venniro M. Persistent palatable food preference in rats with a history of limited and extended access to methamphetamine self-administration. Addict Biol 2015; 20:913-26. [PMID: 25582886 DOI: 10.1111/adb.12220] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent studies have shown that when given a mutually exclusive choice between cocaine and palatable foods, most rats prefer the non-drug rewards over cocaine. Here, we used a discrete choice procedure to assess whether palatable food preference generalizes to rats with a history of limited (3 hours/day) or extended (6 or 9 hours/day) access to methamphetamine self-administration. On different daily sessions, we trained rats to lever-press for either methamphetamine (0.1-0.2 mg/kg/infusion) or palatable food (five pellets per reward delivery) for several weeks; regular food was freely available. We then assessed food-methamphetamine preference either during training, after priming methamphetamine injections (0.5-1.0 mg/kg), following a satiety manipulation (palatable food exposure in the home cage) or after 21 days of withdrawal from methamphetamine. We also assessed progressive ratio responding for palatable food and methamphetamine. We found that independent of the daily drug access conditions and the withdrawal period, the rats strongly preferred the palatable food over methamphetamine, even when they were given free access to the palatable food in the home cage. Intake of methamphetamine and progressive ratio responding for the drug, both of which increased or escalated over time, did not predict preference in the discrete choice test. Results demonstrate that most rats strongly prefer palatable food pellets over intravenous methamphetamine, confirming previous studies using discrete choice procedures with intravenous cocaine. Results also demonstrate that escalation of drug self-administration, a popular model of compulsive drug use, is not associated with a cardinal feature of human addiction of reduced behavioral responding for non-drug rewards.
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Affiliation(s)
- Daniele Caprioli
- Behavioral Neuroscience Research Branch; Intramural Research Program; NIH; DHHS; National Institute on Drug Abuse; Baltimore MD USA
| | - Tamara Zeric
- Behavioral Neuroscience Research Branch; Intramural Research Program; NIH; DHHS; National Institute on Drug Abuse; Baltimore MD USA
| | - Eric B. Thorndike
- Behavioral Neuroscience Research Branch; Intramural Research Program; NIH; DHHS; National Institute on Drug Abuse; Baltimore MD USA
| | - Marco Venniro
- Behavioral Neuroscience Research Branch; Intramural Research Program; NIH; DHHS; National Institute on Drug Abuse; Baltimore MD USA
- Neuropsychopharmacology Laboratory; Section Pharmacology; Department Public Health and Community Medicine; University of Verona; Italy
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27
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Tunstall BJ, Kearns DN. Sign-tracking predicts increased choice of cocaine over food in rats. Behav Brain Res 2014; 281:222-8. [PMID: 25541036 DOI: 10.1016/j.bbr.2014.12.034] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 12/04/2014] [Accepted: 12/15/2014] [Indexed: 10/24/2022]
Abstract
The purpose of this study was to determine whether the tendency to sign-track to a food cue was predictive of rats' choice of cocaine over food. First, rats were trained on a procedure where insertion of a retractable lever was paired with food. A sub-group of rats - sign-trackers - primarily approached and contacted the lever, while another sub-group - goal-trackers - approached the site of food delivery. Rats were then trained on a choice task where they could choose between an infusion of cocaine (1.0 mg/kg) and a food pellet (45 mg). Sign-trackers chose cocaine over food significantly more often than did goal-trackers. These results support the incentive-salience theory of addiction and add to a growing number of studies which suggest that sign-trackers may model an addiction-prone phenotype.
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Tunstall BJ, Riley AL, Kearns DN. Drug specificity in drug versus food choice in male rats. Exp Clin Psychopharmacol 2014; 22:364-72. [PMID: 24886157 PMCID: PMC4156291 DOI: 10.1037/a0037019] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Although different classes of drug differ in their mechanisms of reinforcement and effects on behavior, little research has focused on differences in self-administration behaviors maintained by users of these drugs. Persistent drug choice despite available reinforcement alternatives has been proposed to model behavior relevant to addiction. The present study used a within-subjects procedure, where male rats (Long-Evans, N = 16) were given a choice between cocaine (1.0 mg/kg/infusion) and food (a single 45-mg grain pellet) or between heroin (0.02 mg/kg/infusion) and food in separate phases (drug order counterbalanced). All rats were initially trained to self-administer each drug, and the doses used were based on previous studies showing that small subsets of rats tend to prefer drug over food reinforcement. The goal of the present study was to determine whether rats that prefer cocaine would also prefer heroin. Choice sessions consisted of 2 forced-choice trials with each reinforcer, followed by 14 free-choice trials (all trials separated by 10-min intertrial interval). Replicating previous results, small subsets of rats preferred either cocaine (5 of the 16 rats) or heroin (2 of the 16 rats) to the food alternative. Although 1 of the 16 rats demonstrated a preference for both cocaine and heroin to the food alternative, there was no relationship between degree of cocaine and heroin preference in individual rats. The substance-specific pattern of drug preference observed suggests that at least in this animal model, the tendencies to prefer cocaine or heroin in preference to a nondrug alternative are distinct behavioral phenomena.
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Perry AN, Westenbroek C, Becker JB. The development of a preference for cocaine over food identifies individual rats with addiction-like behaviors. PLoS One 2013; 8:e79465. [PMID: 24260227 PMCID: PMC3832528 DOI: 10.1371/journal.pone.0079465] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 10/01/2013] [Indexed: 11/18/2022] Open
Abstract
RATIONALE Cocaine dependence is characterized by compulsive drug taking that supercedes other recreational, occupational or social pursuits. We hypothesized that rats vulnerable to addiction could be identified within the larger population based on their preference for cocaine over palatable food rewards. OBJECTIVES To validate the choice self-administration paradigm as a preclinical model of addiction, we examined changes in motivation for cocaine and recidivism to drug seeking in cocaine-preferring and pellet-preferring rats. We also examined behavior in males and females to identify sex differences in this "addicted" phenotype. METHODS Preferences were identified during self-administration on a fixed-ratio schedule with cocaine-only, pellet-only and choice sessions. Motivation for each reward was probed early and late during self-administration using a progressive-ratio schedule. Reinstatement of cocaine- and pellet-seeking was examined following exposure to their cues and non-contingent delivery of each reward. RESULTS Cocaine preferring rats increased their drug intake at the expense of pellets, displayed increased motivation for cocaine, attenuated motivation for pellets and greater cocaine and cue-induced reinstatement of drug seeking. Females were more likely to develop cocaine preferences and recidivism of cocaine- and pellet-seeking was sexually dimorphic. CONCLUSIONS The choice self-administration paradigm is a valid preclinical model of addiction. The unbiased selection criteria also revealed sex-specific vulnerability factors that could be differentiated from generalized sex differences in behavior, which has implications for the neurobiology of addiction and effective treatments in each sex.
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Affiliation(s)
- Adam N. Perry
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| | - Christel Westenbroek
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Jill B. Becker
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Psychiatry, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Psychology, University of Michigan, Ann Arbor, Michigan, United States of America
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