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Martins JS, Joyner KJ, McCarthy DM, Morris DH, Patrick CJ, Bartholow BD. Differential brain responses to alcohol-related and natural rewards are associated with alcohol use and problems: Evidence for reward dysregulation. Addict Biol 2022; 27:e13118. [PMID: 34877771 PMCID: PMC8891069 DOI: 10.1111/adb.13118] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 10/15/2021] [Accepted: 11/04/2021] [Indexed: 12/17/2022]
Abstract
Multiple theoretical perspectives posit that drug use leads to biased valuation of drug-related reward, at the expense of naturally occurring rewarding activities (i.e., reward dysregulation). Recent research suggests that the comparative balance of drug-related and nondrug-related reward valuation is a powerful determinant of substance misuse and addiction. We examined differential neurophysiological responses-indexed with the P3 component of the event-related potential (ERP)-elicited by visual alcohol cues and cues depicting natural reward as a neurobiological indicator of problematic drinking. Nondependent, young adult drinkers (N = 143, aged 18-30 years) completed questionnaire measures assessing alcohol use and problems, and viewed alcohol cues (pictures of alcoholic beverages), high-arousing natural reward cues (erotica, adventure scenes), nonalcoholic beverage cues, and neutral scenes (e.g., household items) while ERPs were recorded. When examined separately, associations of P3-ERP reactivity to alcohol cues and natural reward cues with alcohol use and problems were weak. However, differential P3 response to the two types of cues (i.e., reward dysregulation P3) showed consistent and robust associations with all indices of alcohol use and problems and differentiated high-risk from lower-risk drinkers. The current results support the idea that the differential incentive-motivational value of alcohol, relative to naturally rewarding activities, is associated with increased risk for substance misuse and dependence, and highlight a novel neurophysiological indicator-the reward dysregulation P3-of this differential reward valuation.
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Lay BPP, Khoo SYS. Associative processes in addiction relapse models: A review of their Pavlovian and instrumental mechanisms, history, and terminology. NEUROANATOMY AND BEHAVIOUR 2021. [DOI: 10.35430/nab.2021.e18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Animal models of relapse to drug-seeking have borrowed heavily from associative learning approaches. In studies of relapse-like behaviour, animals learn to self-administer drugs then receive a period of extinction during which they learn to inhibit the operant response. Several triggers can produce a recovery of responding which form the basis of a variety of models. These include the passage of time (spontaneous recovery), drug availability (rapid reacquisition), extinction of an alternative response (resurgence), context change (renewal), drug priming, stress, and cues (reinstatement). In most cases, the behavioural processes driving extinction and recovery in operant drug self-administration studies are similar to those in the Pavlovian and behavioural literature, such as context effects. However, reinstatement in addiction studies have several differences with Pavlovian reinstatement, which have emerged over several decades, in experimental procedures, associative mechanisms, and terminology. Interestingly, in cue-induced reinstatement, drug-paired cues that are present during acquisition are omitted during lever extinction. The unextinguished drug-paired cue may limit the model’s translational relevance to cue exposure therapy and renders its underlying associative mechanisms ambiguous. We review major behavioural theories that explain recovery phenomena, with a particular focus on cue-induced reinstatement because it is a widely used model in addiction. We argue that cue-induced reinstatement may be explained by a combination of behavioural processes, including reacquisition of conditioned reinforcement and Pavlovian to Instrumental Transfer. While there are important differences between addiction studies and the behavioural literature in terminology and procedures, it is clear that understanding associative learning processes is essential for studying relapse.
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Affiliation(s)
- Belinda Po Pyn Lay
- Center for Studies in Behavioral Neurobiology/Groupe de Recherche en Neurobiologie Comportementale, Department of Psychology, Concordia University, Montreal, Canada
| | - Shaun Yon-Seng Khoo
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, Quebec, Canada
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Bickel WK, Mellis AM, Snider SE, Athamneh LN, Stein JS, Pope DA. 21st century neurobehavioral theories of decision making in addiction: Review and evaluation. Pharmacol Biochem Behav 2018; 164:4-21. [PMID: 28942119 PMCID: PMC5747999 DOI: 10.1016/j.pbb.2017.09.009] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 08/24/2017] [Accepted: 09/12/2017] [Indexed: 01/21/2023]
Abstract
This review critically examines neurobehavioral theoretical developments in decision making in addiction in the 21st century. We specifically compare each theory reviewed to seven benchmarks of theoretical robustness, based on their ability to address: why some commodities are addictive; developmental trends in addiction; addiction-related anhedonia; self-defeating patterns of behavior in addiction; why addiction co-occurs with other unhealthy behaviors; and, finally, means for the repair of addiction. We have included only self-contained theories or hypotheses which have been developed or extended in the 21st century to address decision making in addiction. We thus review seven distinct theories of decision making in addiction: learning theories, incentive-sensitization theory, dopamine imbalance and systems models, opponent process theory, strength models of self-control failure, the competing neurobehavioral decision systems theory, and the triadic systems theory of addiction. Finally, we have directly compared the performance of each of these theories based on the aforementioned benchmarks, and highlighted key points at which several theories have coalesced.
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Affiliation(s)
- Warren K Bickel
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States; Graduate Program in Translational Biology, Medicine, and Health, Roanoke, VA, United States; Department of Psychology, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States; Department of Neuroscience, Virginia Polytechnic Institute and State University, United States; Faculty of Health Sciences, Virginia Polytechnic Institute and State University, United States; Department of Psychiatry and Behavioral Medicine, Virginia Tech Carilion School of Medicine, United States.
| | - Alexandra M Mellis
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States; Graduate Program in Translational Biology, Medicine, and Health, Roanoke, VA, United States
| | - Sarah E Snider
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States
| | - Liqa N Athamneh
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States; Graduate Program in Translational Biology, Medicine, and Health, Roanoke, VA, United States
| | - Jeffrey S Stein
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States
| | - Derek A Pope
- Addiction Recovery Research Center, Virginia Tech Carilion Research Institute, Roanoke, VA, United States
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Perry CJ, Zbukvic I, Kim JH, Lawrence AJ. Role of cues and contexts on drug-seeking behaviour. Br J Pharmacol 2014; 171:4636-72. [PMID: 24749941 PMCID: PMC4209936 DOI: 10.1111/bph.12735] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 04/04/2014] [Accepted: 04/10/2014] [Indexed: 01/15/2023] Open
Abstract
Environmental stimuli are powerful mediators of craving and relapse in substance-abuse disorders. This review examined how animal models have been used to investigate the cognitive mechanisms through which cues are able to affect drug-seeking behaviour. We address how animal models can describe the way drug-associated cues come to facilitate the development and persistence of drug taking, as well as how these cues are critical to the tendency to relapse that characterizes substance-abuse disorders. Drug-associated cues acquire properties of conditioned reinforcement, incentive motivation and discriminative control, which allow them to influence drug-seeking behaviour. Using these models, researchers have been able to investigate the pharmacology subserving the behavioural impact of environmental stimuli, some of which we highlight. Subsequently, we examine whether the impact of drug-associated stimuli can be attenuated via a process of extinction, and how this question is addressed in the laboratory. We discuss how preclinical research has been translated into behavioural therapies targeting substance abuse, as well as highlight potential developments to therapies that might produce more enduring changes in behaviour.
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Affiliation(s)
- Christina J Perry
- Behavioural Neuroscience Division, The Florey Institute of Neuroscience and Mental HealthParkville, Vic., Australia
- Florey Department of Neuroscience and Mental Health, University of MelbourneParkville, Vic., Australia
| | - Isabel Zbukvic
- Behavioural Neuroscience Division, The Florey Institute of Neuroscience and Mental HealthParkville, Vic., Australia
- Florey Department of Neuroscience and Mental Health, University of MelbourneParkville, Vic., Australia
| | - Jee Hyun Kim
- Behavioural Neuroscience Division, The Florey Institute of Neuroscience and Mental HealthParkville, Vic., Australia
- Florey Department of Neuroscience and Mental Health, University of MelbourneParkville, Vic., Australia
| | - Andrew J Lawrence
- Behavioural Neuroscience Division, The Florey Institute of Neuroscience and Mental HealthParkville, Vic., Australia
- Florey Department of Neuroscience and Mental Health, University of MelbourneParkville, Vic., Australia
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Lucantonio F, Caprioli D, Schoenbaum G. Transition from 'model-based' to 'model-free' behavioral control in addiction: Involvement of the orbitofrontal cortex and dorsolateral striatum. Neuropharmacology 2014; 76 Pt B:407-15. [PMID: 23752095 PMCID: PMC3809026 DOI: 10.1016/j.neuropharm.2013.05.033] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 05/06/2013] [Accepted: 05/15/2013] [Indexed: 01/11/2023]
Abstract
Cocaine addiction is a complex and multidimensional process involving a number of behavioral and neural forms of plasticity. The behavioral transition from voluntary drug use to compulsive drug taking may be explained at the neural level by drug-induced changes in function or interaction between a flexible planning system, associated with prefrontal cortical regions, and a rigid habit system, associated with the striatum. The dichotomy between these two systems is operationalized in computational theory by positing model-based and model-free learning mechanisms, the former relying on an "internal model" of the environment and the latter on pre-computed or cached values to control behavior. In this review, we will suggest that model-free and model-based learning mechanisms appear to be differentially affected, at least in the case of psychostimulants such as cocaine, with the former being enhanced while the latter are disrupted. As a result, the behavior of long-term drug users becomes less flexible and responsive to the desirability of expected outcomes and more habitual, based on the long history of reinforcement. To support our specific proposal, we will review recent neural and behavioral evidence on the effect of psychostimulant exposure on orbitofrontal and dorsolateral striatum structure and function. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Federica Lucantonio
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; NIDA, Intramural Research Program, Baltimore, MD 21224, USA
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Acquisition of responding with a remifentanil-associated conditioned reinforcer in the rat. Psychopharmacology (Berl) 2013; 229:235-43. [PMID: 23609770 PMCID: PMC3757104 DOI: 10.1007/s00213-013-3102-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 03/29/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Drug-associated environmental stimuli may serve as conditioned reinforcers to enhance drug self-administration behaviors in humans and laboratory animals. However, it can be difficult to distinguish experimentally the conditioned reinforcing effects of a stimulus from other behavioral processes that can change rates of responding. OBJECTIVES To characterize the conditioned reinforcing effects of a stimulus paired with the μ-opioid agonist, remifentanil, using a new-response acquisition procedure in the rat. METHODS First, in Pavlovian conditioning (PAV) sessions, rats received response-independent IV injections of remifentanil and presentations of a light-noise compound stimulus. In paired PAV groups, injections and stimulus presentations always co-occurred. In random PAV control groups, injections and stimulus presentations occurred with no consistent relationship. Second, in instrumental acquisition (ACQ) sessions, all animals could respond in an active nose-poke that produced the stimulus alone or in an inactive nose-poke that had no scheduled consequences. RESULTS During ACQ, rats made significantly more active nose-pokes than inactive nose-pokes after paired PAV, but not after random PAV. Between groups, rats also made more active nose-pokes after paired PAV than after random PAV. After paired PAV, increased active responding was obtained under different schedules of reinforcement, persisted across multiple ACQ sessions, and depended on the number of PAV sessions conducted. CONCLUSIONS The remifentanil-paired stimulus served as a conditioned reinforcer for nose-poking: responding depended on both the contingency between the stimulus and remifentanil and the contingency between the nose-poke and the stimulus. Generally, new-response acquisition procedures may provide valid, flexible models for studying opioid-based conditioned reinforcement.
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Limbrick-Oldfield EH, van Holst RJ, Clark L. Fronto-striatal dysregulation in drug addiction and pathological gambling: Consistent inconsistencies? NEUROIMAGE-CLINICAL 2013; 2:385-93. [PMID: 24179792 PMCID: PMC3777686 DOI: 10.1016/j.nicl.2013.02.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 02/20/2013] [Accepted: 02/23/2013] [Indexed: 02/05/2023]
Abstract
Alterations in appetitive processing are central to the major psychological theories of addiction, with differential predictions made by the reward deficiency, incentive salience, and impulsivity hypotheses. Functional MRI has become the chief means of testing these predictions, with experiments reliably highlighting disturbances at the level of the striatum, medial prefrontal cortex, and affiliated regions. However, demonstrations of hypo-reactivity and hyper-reactivity of this circuitry in drug addicted groups are reported in approximately equal measure. Similar findings are echoed in the emergent neuroimaging literature on pathological gambling, which has recently witnessed a coming of age. The first aim of this article is to consider some of the methodological aspects of these experiments that could influence the observed direction of group-level effects, including the baseline condition, trial structure and timing, and the nature of the appetitive cues (drug-related, monetary, or primary rewards). The second aim is to highlight the conceptual traction that is offered by pathological gambling, as a model of a ‘toxicity free’ addiction and an illness where tasks of monetary reinforcement afford a more direct mapping to the abused commodity. Our conclusion is that relatively subtle decisions in task design appear capable of driving group differences in fronto-striatal circuitry in entirely opposing directions, even with tasks and task variants that look ostensibly similar. Differentiation between the psychological theories of addiction will require a greater breadth of experimental designs, with more research needed on processing of primary appetitive cues, aversive processing, and in vulnerable/at-risk groups. We outline the current psychological theories of addiction and their predictions. We review recent fMRI literature of substance addictions and appetitive processing. Reasons for opposing results (hyper- vs hypo-active reward regions) are discussed. Recent fMRI findings of appetitive processing in pathological gambling are reviewed. Pathological gambling is suggested as a prototypical addiction for imaging research.
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Mahler SV, Smith RJ, Moorman DE, Sartor GC, Aston-Jones G. Multiple roles for orexin/hypocretin in addiction. PROGRESS IN BRAIN RESEARCH 2012; 198:79-121. [PMID: 22813971 PMCID: PMC3643893 DOI: 10.1016/b978-0-444-59489-1.00007-0] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Orexins/hypocretins are hypothalamic peptides involved in arousal and wakefulness, but also play a critical role in drug addiction and reward-related behaviors. Here, we review the roles played by orexins in a variety of animal models of drug addiction, emphasizing both commonalities and differences for orexin's involvement in seeking of the major classes of abused drugs, as well as food. One common theme that emerges is an involvement of orexins in drug seeking triggered by external stimuli (e.g., cues, contexts or stressors). We also discuss the functional neuronal circuits in which orexins are embedded, and how these circuits mediate addiction-related behaviors, with particular focus on the role of orexin and glutamate interactions within the ventral tegmental area. Finally, we attempt to contextualize the role of orexins in reward by discussing ways in which these peptides, expressed in only a few thousand neurons in the brain, can have such wide-ranging effects on behavior.
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Affiliation(s)
- Stephen V. Mahler
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Rachel J. Smith
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - David E. Moorman
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Gregory C. Sartor
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Gary Aston-Jones
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
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Cues paired with either rapid or slower self-administered cocaine injections acquire similar conditioned rewarding properties. PLoS One 2011; 6:e26481. [PMID: 22039496 PMCID: PMC3198427 DOI: 10.1371/journal.pone.0026481] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 09/27/2011] [Indexed: 11/19/2022] Open
Abstract
The faster drugs of abuse reach the brain, the more addictive they can be. It is not known why this is. Environmental stimuli associated with drugs can promote the development and persistence of addiction by invigorating and precipitating drug-seeking behaviour. We determined, therefore, whether cues associated with the self-administration of rapidly delivered cocaine (injected intravenously over 5 versus 90 seconds) would acquire greater conditioned rewarding properties, as assessed by the performance of an operant response reinforced solely by the cues. Rats nose-poked for intravenous cocaine infusions delivered either over 5 or 90 seconds. Discrete visual cues accompanied each infusion. The rats could then press a lever to obtain the cues—now a conditioned reward—or an inactive lever. Rats in both the 5- and 90-second groups pressed more on the active versus inactive lever following extensive (24 sessions) but not following limited (3 sessions) self-administration training. There were no group differences in this behaviour. Following withdrawal from cocaine self-administration, lever discrimination progressively abated in both groups and was lost by withdrawal day 30. However, the rewarding properties of the cues were not “forgotten” because on withdrawal days 32–33, amphetamine selectively enhanced active-lever pressing, and did so to a similar extent in both groups. Thus, cues paired with rapid or slower cocaine delivery acquire similar conditioned rewarding properties. We conclude, therefore, that the rapid delivery of cocaine to the brain promotes addiction by mechanisms that might not involve a greater ability of drug cues to control behaviour.
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Triadimefon supports conditioned cue preference. Behav Brain Res 2011; 221:307-10. [DOI: 10.1016/j.bbr.2011.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 02/27/2011] [Accepted: 03/03/2011] [Indexed: 11/22/2022]
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Scibelli AC, McKinnon CS, Reed C, Burkhart-Kasch S, Li N, Baba H, Wheeler JM, Phillips TJ. Selective breeding for magnitude of methamphetamine-induced sensitization alters methamphetamine consumption. Psychopharmacology (Berl) 2011; 214:791-804. [PMID: 21088960 PMCID: PMC3320759 DOI: 10.1007/s00213-010-2086-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 10/30/2010] [Indexed: 02/06/2023]
Abstract
RATIONALE Genetically determined differences in susceptibility to drug-induced sensitization could be related to risk for drug consumption. OBJECTIVES Studies were performed to determine whether selective breeding could be used to create lines of mice with different magnitudes of locomotor sensitization to methamphetamine (MA). MA sensitization (MASENS) lines were also examined for genetically correlated responses to MA. METHODS Beginning with the F2 cross of C57BL/6J and DBA/2J strains, mice were tested for locomotor sensitization to repeated injections of 1 mg/kg MA and bred based on magnitude of sensitization. Five selected offspring generations were tested. All generations were also tested for MA consumption, and some were tested for dose-dependent locomotor-stimulant responses to MA, consumption of saccharin, quinine, and potassium chloride as a measure of taste sensitivity, and MA clearance after acute and repeated MA. RESULTS Selective breeding resulted in creation of two lines [MA high sensitization (MAHSENS) and MA low sensitization (MALSENS)] that differed in magnitude of MA-induced sensitization. Initially, greater MA consumption in MAHSENS mice reversed over the course of selection so that MALSENS mice consumed more MA. MAHSENS mice exhibited greater sensitivity to the acute stimulant effects of MA, but there were no significant differences between the lines in MA clearance from blood. CONCLUSIONS Genetic factors influence magnitude of MA-induced locomotor sensitization and some of the genes involved in magnitude of this response also influence MA sensitivity and consumption. Genetic factors leading to greater MA-induced sensitization may serve a protective role against high levels of MA consumption.
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Affiliation(s)
- Angela C. Scibelli
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Carrie S. McKinnon
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Cheryl Reed
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Sue Burkhart-Kasch
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Na Li
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Harue Baba
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Jeanna M. Wheeler
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA
| | - Tamara J. Phillips
- Department of Behavioral Neuroscience and Methamphetamine Abuse Research Center, Oregon Health & Science University, and Veterans Affairs Medical Center, Portland, OR, USA. Portland VA Medical Center, 3710 SW US Veterans Hospital Rd., R&D-32, Portland, OR 97239, USA
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Mahler SV, Berridge KC. Which cue to "want?" Central amygdala opioid activation enhances and focuses incentive salience on a prepotent reward cue. J Neurosci 2009; 29:6500-13. [PMID: 19458221 PMCID: PMC2802210 DOI: 10.1523/jneurosci.3875-08.2009] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Revised: 03/24/2009] [Accepted: 04/03/2009] [Indexed: 12/31/2022] Open
Abstract
The central nucleus of the amygdala (CeA) helps translate learning into motivation, and here, we show that opioid stimulation of CeA magnifies and focuses learned incentive salience onto a specific reward cue (pavlovian conditioned stimulus, or CS). This motivation enhancement makes that cue more attractive, noticeable, and liable to elicit appetitive and consummatory behaviors. To reveal the focusing of incentive salience, we exploited individual differences in an autoshaping paradigm in which a rat prefers to approach, nibble, and sniff one of two reward-associated stimuli (its prepotent stimulus). The individually prepotent cue is either a predictive CS+ that signals reward (8 s metal lever insertion) or instead the metal cup that delivers sucrose pellets (the reward source). Results indicated that CeA opioid activation by microinjection of the mu agonist DAMGO (0.1 microg) selectively and reversibly enhanced the attractiveness of whichever reward CS was that rat's prepotent cue. CeA DAMGO microinjections made rats more vigorously approach their particular prepotent CS and to energetically sniff and nibble it in a nearly frenzied consummatory manner. Only the prepotent cue was enhanced as an incentive target, and alternative cues were not enhanced. Conversely, inactivation of CeA by muscimol microinjection (0.25 microg) suppressed approach, nibbles, and sniffs of the prepotent CS. Confirming modulation of incentive salience, unconditioned food intake was similarly increased by DAMGO microinjection and decreased by muscimol in CeA. We conclude that opioid neurotransmission in CeA helps determine which environmental stimuli become most "wanted," and how "wanted" they become. This may powerfully guide reward-seeking behavior.
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Affiliation(s)
- Stephen V Mahler
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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Abstract
Cocaine sensitization is produced by repeated exposure to the drug and is thought to reflect neuroadaptations that contribute to addiction. Here, we identify the Ca(2+)/calmodulin-stimulated adenylyl cyclases, type 1 (AC1) and type 8 (AC8), as novel regulators of this behavioral plasticity. We show that, whereas AC1 and AC8 single knock-out mice (AC1(-/-) and AC8(-/-)) exhibit Ca(2+)-stimulated adenylyl cyclase activity in striatal membrane fractions, AC1/8 double-knock-out (DKO) mice do not. Furthermore, DKO mice are acutely supersensitive to low doses of cocaine and fail to display locomotor sensitization after chronic cocaine treatment. Because of the known role for the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase signaling pathway in cocaine-induced behavioral plasticity and its coupling to calcium-stimulated cAMP signaling in the hippocampus, we measured phosphorylated ERK (pERK) levels in the striatum. Under basal conditions, pERK is upregulated in choline acetyltransferase-positive interneurons in DKO mice relative to wild-type (WT) controls. After acute cocaine treatment, pERK signaling is significantly suppressed in medium spiny neurons (MSNs) of DKO mice relative to WT mice. In addition to the lack of striatal ERK activation by acute cocaine, signaling machinery downstream of ERK is uncoupled in DKO mice. We demonstrate that AC1 and AC8 are necessary for the phosphorylation of mitogen and stress-activated kinase-1 (pMSK1) at Ser376 and Thr581 and cAMP response element-binding protein (pCREB) at Ser133 after acute cocaine treatment. Our results demonstrate that the Ca(2+)-stimulated adenylyl cyclases regulate long-lasting cocaine-induced behavioral plasticity via activation of the ERK/MSK1/CREB signaling pathway in striatonigral MSNs.
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Robinson TE, Berridge KC. Review. The incentive sensitization theory of addiction: some current issues. Philos Trans R Soc Lond B Biol Sci 2008; 363:3137-46. [PMID: 18640920 DOI: 10.1098/rstb.2008.0093] [Citation(s) in RCA: 1040] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We present a brief overview of the incentive sensitization theory of addiction. This posits that addiction is caused primarily by drug-induced sensitization in the brain mesocorticolimbic systems that attribute incentive salience to reward-associated stimuli. If rendered hypersensitive, these systems cause pathological incentive motivation ('wanting') for drugs. We address some current questions including: what is the role of learning in incentive sensitization and addiction? Does incentive sensitization occur in human addicts? Is the development of addiction-like behaviour in animals associated with sensitization? What is the best way to model addiction symptoms using animal models? And, finally, what are the roles of affective pleasure or withdrawal in addiction?
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Affiliation(s)
- Terry E Robinson
- Department of Psychology, Biopsychology Program, The University of Michigan, East Hall, 530 Church Street, Ann Arbor, MI 48109-1109, USA.
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