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Calma ID, Persons AL, Napier TC. Mitochondrial function influences expression of methamphetamine-induced behavioral sensitization. Sci Rep 2021; 11:24529. [PMID: 34972820 PMCID: PMC8720100 DOI: 10.1038/s41598-021-04301-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 12/13/2021] [Indexed: 12/21/2022] Open
Abstract
Repeated methamphetamine use leads to long lasting brain and behavioral changes in humans and laboratory rats. These changes have high energy requirements, implicating a role for mitochondria. We explored whether mitochondrial function underpins behaviors that occur in rats months after stopping methamphetamine self-administration. Accordingly, rats self-administered intravenous methamphetamine for 3 h/day for 14 days. The mitochondrial toxin rotenone was administered as (1 mg/kg/day for 6 days) via an osmotic minipump starting at 0, 14 or 28 days of abstinence abstinence. On abstinence day 61, expression of methamphetamine-induced behavioral sensitization was obtained with an acute methamphetamine challenge in rotenone-free rats. Rotenone impeded the expression of sensitization, with the most robust effects obtained with later abstinence exposure. These findings verified that self-titration of moderate methamphetamine doses results in behavioral (and thus brain) changes that can be revealed months after exposure termination, and that the meth-initiated processes progressed during abstinence so that longer abstinence periods were more susceptible to the consequences of exposure to a mitochondrial toxin.
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Affiliation(s)
- I. Daphne Calma
- grid.240684.c0000 0001 0705 3621Departments of Psychiatry and Behavioral Sciences, Rush University Medical Center, Chicago, IL 60612 USA ,grid.240684.c0000 0001 0705 3621Center for Compulsive Behavior and Addiction, Rush University Medical Center, Chicago, IL 60612 USA
| | - Amanda L. Persons
- grid.240684.c0000 0001 0705 3621Departments of Psychiatry and Behavioral Sciences, Rush University Medical Center, Chicago, IL 60612 USA ,grid.240684.c0000 0001 0705 3621Departments of Physician Assistant Studies, Rush University Medical Center, Chicago, IL 60612 USA ,grid.240684.c0000 0001 0705 3621Center for Compulsive Behavior and Addiction, Rush University Medical Center, Chicago, IL 60612 USA
| | - T. Celeste Napier
- grid.240684.c0000 0001 0705 3621Departments of Psychiatry and Behavioral Sciences, Rush University Medical Center, Chicago, IL 60612 USA ,grid.240684.c0000 0001 0705 3621Center for Compulsive Behavior and Addiction, Rush University Medical Center, Chicago, IL 60612 USA ,grid.240684.c0000 0001 0705 3621Department of Psychiatry and Behavioral Sciences, Rush University Medical Center, Suite 424, Cohn Research Building, 1735 W. Harrison Street, Chicago, IL 60610 USA
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Madayag AC, Gomez D, Anderson EM, Ingebretson AE, Thomas MJ, Hearing MC. Cell-type and region-specific nucleus accumbens AMPAR plasticity associated with morphine reward, reinstatement, and spontaneous withdrawal. Brain Struct Funct 2019; 224:2311-2324. [PMID: 31201496 PMCID: PMC6698404 DOI: 10.1007/s00429-019-01903-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 06/04/2019] [Indexed: 12/17/2022]
Abstract
Despite evidence that morphine-related pathologies reflect adaptations in NAc glutamate signaling, substantial gaps in basic information remain. The current study examines the impact of non-contingent acute, repeated, and withdrawal-inducing morphine dosing regimens on glutamate transmission in D1- or D2-MSNs in the nucleus accumbens shell (NAcSh) and core (NAcC) sub-regions in hopes of identifying excitatory plasticity that may contribute to unique facets of opioid addiction-related behavior. Following an acute morphine injection (10 mg/kg), average miniature excitatory postsynaptic current (mEPSC) amplitude mediated by AMPA-type glutamate receptors was increased at D1-MSNs in the both the NAcShl and NAcC, whereas only the frequency of events was elevated at D2-MSNs in the NAcSh. In contrast, spontaneous somatic withdrawal induced by escalating dose of repeated morphine twice per day (20, 40, 60, 80, 100 mg/kg) enhanced mEPSC frequency specifically at D2-MSNs in the NAcSh. Similar to previous findings, excitatory drive was elevated at NAcSh D1-MSNs after 10-14 days home cage abstinence. Following abstinence, an acute drug re-exposure produced a rapid and enduring endocytosis of GluA2-containing AMPARs at D1-MSNs in the shell, that when blocked by an intra-NAc shell infusion of the Tat-GluA23Y peptide, increased reinstatement of morphine place preference-a phenomenon distinctly different than effects previously found with cocaine. The present study is the first to directly identify unique circuit specific adaptations in NAc glutamate synaptic transmission associated with morphine-related acute reward and somatic withdrawal as well as post-abstinence short-term plasticity. Moreover, while differing classes of abused drugs (i.e., psychostimulants and opioids) produce seemingly similar bidirectional plasticity in the NAc following drug re-exposure, our findings indicate this plasticity has distinct behavioral consequences.
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Affiliation(s)
- Aric C Madayag
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, 53233, USA
| | - Devan Gomez
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, 53233, USA
| | - Eden M Anderson
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, 53233, USA
| | - Anna E Ingebretson
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Mark J Thomas
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Matthew C Hearing
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, 53233, USA.
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3
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Hearing M. Prefrontal-accumbens opioid plasticity: Implications for relapse and dependence. Pharmacol Res 2018; 139:158-165. [PMID: 30465850 DOI: 10.1016/j.phrs.2018.11.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 11/05/2018] [Accepted: 11/07/2018] [Indexed: 01/12/2023]
Abstract
In addiction, an individual's ability to inhibit drug seeking and drug taking is thought to reflect a pathological strengthening of drug-seeking behaviors or impairments in the capacity to control maladaptive behavior. These processes are not mutually exclusive and reflect drug-induced modifications within prefrontal cortical and nucleus accumbens circuits, however unlike psychostimulants such as cocaine, far less is known about the temporal, anatomical, and cellular dynamics of these changes. We discuss what is known regarding opioid-induced adaptations in intrinsic membrane physiology and pre-/postsynaptic neurotransmission in principle pyramidal and medium spiny neurons in the medial prefrontal cortex and nucleus accumbens from electrophysiological studies and explore how circuit specific adaptations may contribute to unique facets of opioid addiction.
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Affiliation(s)
- Matthew Hearing
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, 53233, USA.
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Wilson KE, Limburg S, Duggan MK, Lawther AJ, Williams SJ, Lawrence AJ, Hale MW, Djouma E. The galanin receptor-3 antagonist, SNAP 37889, inhibits cue-induced reinstatement of alcohol-seeking and increases c-Fos expression in the nucleus accumbens shell of alcohol-preferring rats. J Psychopharmacol 2018; 32:911-921. [PMID: 29926762 DOI: 10.1177/0269881118780015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION This study aimed to investigate the effects of the galanin-3 receptor antagonist, SNAP 37889, on c-Fos protein expression after cue-induced reinstatement of alcohol-seeking in the brains of alcohol-preferring rats. METHODS Eighteen alcohol-preferring rats were trained to self-administer 10% v/v ethanol in the presence of response-contingent cues, which was followed by extinction. Rats were then treated with SNAP 37889 (30 mg/kg, i.p.) or vehicle, before being tested for cue-induced reinstatement. Administration of SNAP 37889 reduced cue-induced reinstatement of ethanol-seeking behaviour. To examine the effect of SNAP 37889 and cue-induced reinstatement on neuronal activation, c-Fos expression was measured in subregions of the medial prefrontal cortex and nucleus accumbens. RESULTS SNAP 37889 administration increased c-Fos immunoreactivity in the nucleus accumbens shell, but was without effect in the nucleus accumbens core and the medial prefrontal cortex. Dual-label Fos/tyrosine hydroxylase immunohistochemistry was used to examine the effects of SNAP 37889 on dopamine neurons in the ventral tegmental area; however, no differences between SNAP 37889 and vehicle-treated rats were found. CONCLUSIONS These data support previous findings of galanin-3 receptor involvement in cue-induced reinstatement of alcohol-seeking behaviour, and provide novel evidence that the ability of galanin-3 receptor antagonism to attenuate cue-induced reinstatement relates to activation of the nucleus accumbens shell.
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Affiliation(s)
- Kira-Elise Wilson
- 1 School of Psychology and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Sigrid Limburg
- 1 School of Psychology and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Melissa K Duggan
- 1 School of Psychology and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Adam J Lawther
- 1 School of Psychology and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Spencer J Williams
- 2 School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, VIC, Australia
| | - Andrew J Lawrence
- 3 Florey Institute of Neuroscience and Mental Health, University of Melbourne, VIC, Australia
| | - Matthew W Hale
- 1 School of Psychology and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Elvan Djouma
- 4 School of Life Sciences, La Trobe University, Melbourne, VIC, Australia
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Frazer KM, Richards Q, Keith DR. The long-term effects of cocaine use on cognitive functioning: A systematic critical review. Behav Brain Res 2018; 348:241-262. [PMID: 29673580 DOI: 10.1016/j.bbr.2018.04.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 04/03/2018] [Accepted: 04/04/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND The predominant view of chronic cocaine use maintains that it causes a broad range of cognitive deficits. However, concerns about the possibly deleterious impact of cocaine on cognitive functioning have yet to be thoroughly vetted. This review addresses the impact of cocaine use on such cognitive domains as executive function, memory, language, and psychomotor speed. Additionally, relevant neuroimaging data is considered to understand the neural basis underlying cocaine-related effects on cognitive functioning. METHODS We searched PubMed, Google Scholar, and Embase using the search terms "cocaine and cognition," "cocaine and cognitive functioning," and "cocaine and cognitive deficits or impairment." To meet inclusion criteria we evaluated only cognitive and neuroimaging studies describing the long-term effects of cocaine on cognitive functioning published from 1999 to 2016. RESULTS The majority of studies reported statistically significant differences between cocaine users and non-drug-using controls in brain structures, blood-oxygen-level dependent signals, and brain metabolism. However, differences in cognitive performance were observed on a minority of measures. Additionally, the majority of studies were not compared against normative data. CONCLUSIONS The current evidence does not support the view that chronic cocaine use is associated with broad cognitive deficits. The view that cocaine users have broad cognitive deficits is inaccurate based upon current evidence, and the perpetuation of this view may have negative implications for treatment programs and development of public policies.
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Affiliation(s)
- Kirsten M Frazer
- Department of Psychology, Columbia University, 1190 Amsterdam Ave., New York, NY 10027, USA.
| | - Qwynten Richards
- Department of Psychology, Columbia University, 1190 Amsterdam Ave., New York, NY 10027, USA
| | - Diana R Keith
- Department of Psychiatry, University of Vermont Medical Center, 1 South Prospect Street, Burlington, VT 05401, USA
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Hearing M, Graziane N, Dong Y, Thomas MJ. Opioid and Psychostimulant Plasticity: Targeting Overlap in Nucleus Accumbens Glutamate Signaling. Trends Pharmacol Sci 2018; 39:276-294. [PMID: 29338873 DOI: 10.1016/j.tips.2017.12.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/11/2017] [Accepted: 12/13/2017] [Indexed: 12/11/2022]
Abstract
Commonalities in addictive behavior, such as craving, stimuli-driven drug seeking, and a high propensity for relapse following abstinence, have pushed for a unified theory of addiction that encompasses most abused substances. This unitary theory has recently been challenged - citing distinctions in structural neural plasticity, biochemical signaling, and neural circuitry to argue that addiction to opioids and psychostimulants is behaviorally and neurobiologically distinct. Recent more selective examination of drug-induced plasticity has highlighted that these two drug classes promote an overall reward circuitry signaling overlap through modifying excitatory synapses in the nucleus accumbens - a key constituent of the reward system. We discuss adaptations in presynaptic/postsynaptic and extrasynaptic glutamate signaling produced by opioids and psychostimulants, and their relevance to circuit remodeling and addiction-related behavior - arguing that these core neural adaptations are important targets for developing pharmacotherapies to treat addiction to multiple drugs.
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Affiliation(s)
- Matthew Hearing
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI 53233, USA.
| | - Nicholas Graziane
- Department of Anesthesiology and Perioperative Medicine, Penn State College of Medicine, Hershey, PA 17033, USA; Departments of Neuroscience and Psychiatry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Yan Dong
- Departments of Neuroscience and Psychiatry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Mark J Thomas
- Department of Psychology, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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7
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Fattore L, Diana M. Drug addiction: An affective-cognitive disorder in need of a cure. Neurosci Biobehav Rev 2016; 65:341-61. [DOI: 10.1016/j.neubiorev.2016.04.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 03/24/2016] [Accepted: 04/11/2016] [Indexed: 12/22/2022]
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Cocaine and Amphetamine Induce Overlapping but Distinct Patterns of AMPAR Plasticity in Nucleus Accumbens Medium Spiny Neurons. Neuropsychopharmacology 2016; 41:464-76. [PMID: 26068728 PMCID: PMC5130122 DOI: 10.1038/npp.2015.168] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/24/2015] [Accepted: 05/10/2015] [Indexed: 01/01/2023]
Abstract
Repeated exposure to psychostimulant drugs such as cocaine or amphetamine can promote drug-seeking and -taking behavior. In rodent addiction models, persistent changes in excitatory glutamatergic neurotransmission in the nucleus accumbens (NAc) appear to drive this drug-induced behavioral plasticity. To study whether changes in glutamatergic signaling are shared between or exclusive to specific psychostimulant drugs, we examined synaptic transmission from mice following repeated amphetamine or cocaine administration. Synaptic transmission mediated by AMPA-type glutamate receptors was potentiated in the NAc shell 10-14 days following repeated amphetamine or cocaine treatment. This synaptic enhancement was depotentiated by re-exposure to amphetamine or cocaine. By contrast, in the NAc core only repeated cocaine exposure enhanced synaptic transmission, which was subsequently depotentiated by an additional cocaine but not amphetamine injection during drug abstinence. To better understand the drug-induced depotentiation, we replicated these in vivo findings using an ex vivo model termed 'challenge in the bath,' and showed that drug-induced decreases in synaptic strength occur rapidly (within 30 min) and require activation of metabotropic glutamate receptor 5 (mGluR5) and protein synthesis in the NAc shell, but not NAc core. Overall, these data demonstrate the specificity of neuronal circuit changes induced by amphetamine, introduce a novel method for studying drug challenge-induced plasticity, and define NAc shell medium spiny neurons as a primary site of persistent AMPA-type glutamate receptor plasticity by two widely used psychostimulant drugs.
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9
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DAT isn't all that: cocaine reward and reinforcement require Toll-like receptor 4 signaling. Mol Psychiatry 2015; 20:1525-37. [PMID: 25644383 PMCID: PMC4523496 DOI: 10.1038/mp.2014.177] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 10/16/2014] [Accepted: 11/12/2014] [Indexed: 01/13/2023]
Abstract
The initial reinforcing properties of drugs of abuse, such as cocaine, are largely attributed to their ability to activate the mesolimbic dopamine system. Resulting increases in extracellular dopamine in the nucleus accumbens (NAc) are traditionally thought to result from cocaine's ability to block dopamine transporters (DATs). Here we demonstrate that cocaine also interacts with the immunosurveillance receptor complex, Toll-like receptor 4 (TLR4), on microglial cells to initiate central innate immune signaling. Disruption of cocaine signaling at TLR4 suppresses cocaine-induced extracellular dopamine in the NAc, as well as cocaine conditioned place preference and cocaine self-administration. These results provide a novel understanding of the neurobiological mechanisms underlying cocaine reward/reinforcement that includes a critical role for central immune signaling, and offer a new target for medication development for cocaine abuse treatment.
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10
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Dash S, Balasubramaniam M, Villalta F, Dash C, Pandhare J. Impact of cocaine abuse on HIV pathogenesis. Front Microbiol 2015; 6:1111. [PMID: 26539167 PMCID: PMC4611962 DOI: 10.3389/fmicb.2015.01111] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 09/25/2015] [Indexed: 12/13/2022] Open
Abstract
Over 1.2 million people in the United States are infected with the human immunodeficiency virus type 1 (HIV-1). Tremendous progress has been made over the past three decades on many fronts in the prevention and treatment of HIV-1 disease. However, HIV-1 infection is incurable and antiretroviral drugs continue to remain the only effective treatment option for HIV infected patients. Unfortunately, only three out of ten HIV-1 infected individuals in the US have the virus under control. Thus, majority of HIV-1 infected individuals in the US are either unaware of their infection status or not connected/retained to care or are non-adherent to antiretroviral therapy (ART). This national public health crisis, as well as the ongoing global HIV/AIDS pandemic, is further exacerbated by substance abuse, which serves as a powerful cofactor at every stage of HIV/AIDS including transmission, diagnosis, pathogenesis, and treatment. Clinical studies indicate that substance abuse may increase viral load, accelerate disease progression and worsen AIDS-related mortality even among ART-adherent patients. However, confirming a direct causal link between substance abuse and HIV/AIDS in human patients remains a highly challenging endeavor. In this review we will discuss the recent and past developments in clinical and basic science research on the effects of cocaine abuse on HIV-1 pathogenesis.
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Affiliation(s)
- Sabyasachi Dash
- Center for AIDS Health Disparities Research, Meharry Medical College , Nashville, TN, USA ; School of Graduate Studies and Research, Meharry Medical College , Nashville, TN, USA
| | - Muthukumar Balasubramaniam
- Center for AIDS Health Disparities Research, Meharry Medical College , Nashville, TN, USA ; Department of Biochemistry and Cancer Biology, Meharry Medical College , Nashville, TN, USA
| | - Fernando Villalta
- Center for AIDS Health Disparities Research, Meharry Medical College , Nashville, TN, USA ; School of Graduate Studies and Research, Meharry Medical College , Nashville, TN, USA ; Department of Microbiology and Immunology, Meharry Medical College , Nashville, TN, USA
| | - Chandravanu Dash
- Center for AIDS Health Disparities Research, Meharry Medical College , Nashville, TN, USA ; School of Graduate Studies and Research, Meharry Medical College , Nashville, TN, USA ; Department of Biochemistry and Cancer Biology, Meharry Medical College , Nashville, TN, USA
| | - Jui Pandhare
- Center for AIDS Health Disparities Research, Meharry Medical College , Nashville, TN, USA ; School of Graduate Studies and Research, Meharry Medical College , Nashville, TN, USA ; Department of Microbiology and Immunology, Meharry Medical College , Nashville, TN, USA
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Abstract
Exposure to drugs of abuse, such as cocaine, leads to plastic changes in the activity of brain circuits, and a prevailing view is that these changes play a part in drug addiction. Notably, there has been intense focus on drug-induced changes in synaptic excitability and much less attention on intrinsic excitability factors (that is, excitability factors that are remote from the synapse). Accumulating evidence now suggests that intrinsic factors such as K+ channels are not only altered by cocaine but may also contribute to the shaping of the addiction phenotype.
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12
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Jiang Q, Wang CM, Fibuch EE, Wang JQ, Chu XP. Differential regulation of locomotor activity to acute and chronic cocaine administration by acid-sensing ion channel 1a and 2 in adult mice. Neuroscience 2013; 246:170-8. [PMID: 23644053 DOI: 10.1016/j.neuroscience.2013.04.059] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 04/18/2013] [Accepted: 04/28/2013] [Indexed: 12/12/2022]
Abstract
Acid-sensing ion channels (ASICs) are densely expressed in the brain with ASIC1a and ASIC2 channels being the predominant subtypes. These channels are enriched at synaptic sites and are central for the regulation of normal synaptic transmission. Moreover, increasing evidence links ASICs to the pathogenesis of various neurological and neuropsychiatric disorders. In this study, we explore the putative role of ASIC1a and ASIC2 in the regulation of behavioral sensitivity to the psychostimulant cocaine by utilizing ASIC1a or ASIC2 knockout mice. Acute cocaine injection induced a typical dose-dependent increase in locomotor activities in wild-type (WT) mice. However, in ASIC1a and ASIC2 mutant mice, different motor responses to cocaine were observed. In ASIC1a(-/-) mice, cocaine induced a significantly less motor response at all doses (5, 10, 20, and 30 mg/kg), while in ASIC2(-/-) mice, cocaine (5-20 mg/kg) stimulated locomotor activity to an extent comparable to WT mice. Only at 30 mg/kg, the cocaine-stimulated motor activity was reduced in ASIC2(-/-) mice. In a chronic cocaine administration model (20mg/kg, once daily for 5 days), a challenge injection of cocaine (10mg/kg, after 2-week withdrawal) caused an evident behavioral sensitization in the cocaine-pretreated WT mice. This behavioral sensitization to challenge cocaine was also displayed in ASIC1a(-/-) and ASIC2(-/-) mice. However, ASIC2(-/-) mice showed less sensitization to challenge cocaine when compared to WT and ASIC1a(-/-) mice. Our results demonstrate the important role of ASIC1a and ASIC2 channels in the modulation of behavioral sensitivity to cocaine. The two synapse-enriched ASIC subtypes are believed to play distinguishable roles in the regulation of behavioral responses to acute and chronic cocaine administration.
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Affiliation(s)
- Q Jiang
- Department of Basic Medical Science, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA
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13
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Giza JI, Jung Y, Jeffrey RA, Neugebauer NM, Picciotto MR, Biederer T. The synaptic adhesion molecule SynCAM 1 contributes to cocaine effects on synapse structure and psychostimulant behavior. Neuropsychopharmacology 2013; 38:628-38. [PMID: 23169347 PMCID: PMC3572459 DOI: 10.1038/npp.2012.226] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 10/17/2012] [Accepted: 10/18/2012] [Indexed: 11/09/2022]
Abstract
Drugs of abuse have acute and persistent effects on synapse structure and addiction-related behaviors. Trans-synaptic interactions can control synapse development, and synaptic cell adhesion molecule (SynCAM) proteins (also named nectin-like molecules) are immunoglobulin adhesion proteins that span the synaptic cleft and induce excitatory synapses. Our studies now reveal that the loss of SynCAM 1 in knockout (KO) mice reduces excitatory synapse number in nucleus accumbens (NAc). SynCAM 1 additionally contributes to the structural remodeling of NAc synapses in response to the psychostimulant cocaine. Specifically, we find that cocaine administration increases the density of stubby spines on medium spiny neurons in NAc, and that maintaining this increase requires SynCAM 1. Furthermore, mushroom-type spines on these neurons are structurally more plastic when SynCAM 1 is absent, and challenging drug-withdrawn mice with cocaine shortens these spines in SynCAM 1 KO mice. These effects are correlated with changes on the behavioral level, where SynCAM 1 contributes to the psychostimulant effects of cocaine as measured after acute and repeated administration, and in drug-withdrawn mice. Together, our results provide evidence that the loss of a synapse-organizing adhesion molecule can modulate cocaine effects on spine structures in NAc and increases vulnerability to the behavioral actions of cocaine. SynCAM-dependent pathways may therefore represent novel points of therapeutic intervention after exposure to drugs of abuse.
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Affiliation(s)
- Joanna I Giza
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Yonwoo Jung
- Department of Psychiatry, Yale University Medical School, Yale University, New Haven, CT, USA
| | - Rachel A Jeffrey
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Nichole M Neugebauer
- Department of Psychiatry, Yale University Medical School, Yale University, New Haven, CT, USA
| | - Marina R Picciotto
- Department of Psychiatry, Yale University Medical School, Yale University, New Haven, CT, USA
| | - Thomas Biederer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
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14
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Abstract
Substance dependence is characterized by a group of symptoms, according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR). These symptoms include tolerance, withdrawal, drug consumption for alleviating withdrawal, exaggerated consumption beyond original intention, failure to reduce drug consumption, expending a considerable amount of time obtaining or recovering from the substance's effects, disregard of basic aspects of life (for example, family), and maintenance of drug consumption, despite facing adverse consequences. The nucleus accumbens (NAc) is a brain structure located in the basal forebrain of vertebrates, and it has been the target of addictive drugs. Different neurotransmitter systems at the level of the NAc circuitry have been linked to the different problems of drug addiction, like compulsive use and relapse. The glutamate system has been linked mainly to relapse after drug-seeking extinction. The dopamine system has been linked mainly to compulsive drug use. The glutamate homeostasis hypothesis centers around the dynamics of synaptic and extrasynaptic levels of glutamate, and their impact on circuitry from the prefrontal cortex (PFC) to the NAc. After repetitive drug use, deregulation of this homeostasis increases the release of glutamate from the PFC to the NAc during drug relapse. Glial cells also play a fundamental role in this hypothesis; glial cells shape the interactions between the PFC and the NAc by means of altering glutamate levels in synaptic and extrasynaptic spaces. On the other hand, cocaine self-administration and withdrawal increases the surface expression of subunit glutamate receptor 1 (GluA1) of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors at the level of the NAc. Also, cocaine self-administration and withdrawal induce the formation of subunit glutamate receptor 2 (GluA2), lacking the Ca(2+)-permeable AMPA receptors (CP-AMPARs) at the level of the NAc. Antagonism of the CP-AMPARs reduces cravings. It is necessary to pursue further exploration of the AMPA receptor subunit composition and variations at the level of the NAc for a better understanding of glutamatergic plastic changes. It is known that cocaine and morphine are able to induce changes in dendritic spine morphology by modifying actin cycling. These changes include an initial increase in spine head diameter and increases in AMPA receptor expression, followed by a second stage of spine head diameter retraction and reduction of the AMPA receptors' expression in spines. Besides glutamate and dopamine, other factors, like brain-derived neurotrophic factor (BDNF), can influence NAc activity and induce changes in dendritic spine density. BDNF also induces drug-related behaviors like self-administration and relapse. Neither apoptosis nor neurogenesis plays a relevant role in the neurobiological processes subjacent to cocaine addiction in adults (rodent or human). Different therapeutic drugs like N-acetylcysteine (NAC), modafinil, acamprosate, and topiramate have been tested in preclinical and/or clinical models for alleviating drug relapse. Moreover, these therapeutic drugs target the glutamatergic circuitry between the PFC and the NAc. NAC and acamprosate have shown inconsistent results in clinical trials. Modafinil and topiramate have shown some success, but more clinical trials are necessary. Based on the current review findings, it could be recommendable to explore therapeutic approaches that include synergism between different drugs and neurotransmitter systems. The discrepancy in the results of some therapeutic drugs between preclinical versus clinical trials for alleviating relapse or drug dependence could be linked to the scarce exploration of preclinical models that mimic polydrug abuse patterns, for example, cocaine plus alcohol. At the clinical level, the pattern of polydrug consumption is a phenomenon of considerable frequency. Finally, as a complement at the end, an updated summary is included about the role of glutamate in other neuropsychiatric disorders (for example, mood disorders, schizophrenia, and others).
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Affiliation(s)
- Gabriel C Quintero
- Florida State University - Panama, Clayton, Panama ; Medical University of South Carolina, Charleston, South Carolina, USA ; Smithsonian Tropical Research Institute, Ancon, Republic of Panama
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15
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Abstract
Drug and alcohol addiction is a debilitating disorder characterized by persistent drug-seeking behaviors despite negative physiological, medical, or social consequences. Neurobiological models of addiction propose that the reinforcing effects of addictive drugs are associated with altered neurotransmission within the reward 'mesocorticolimbic' circuitry in the brain. Immense efforts are therefore designed to target the mesocorticolimbic circuitry in attenuating drug dependence and addiction-related behaviors. Yet, to date, most addiction treatments have demonstrated only limited success in reducing addiction-related behaviors. Accumulating and compelling evidence suggests that novel nonsurgical brain stimulation techniques, such as transcranial magnetic stimulation and transcranial direct current stimulation, could serve as promising tools for indexing altered neurotransmission associated with repetitive drug use, and moreover, may hold therapeutic potential for the treatment of drug dependence and addiction-related behaviors. This chapter reviews and discusses the current and potential applications of such techniques in the study and treatment of addiction; we focus on a number of common drugs of abuse, including nicotine, alcohol, cocaine, cannabis, and ecstasy.
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Ma L, Wu YM, Guo YY, Yang Q, Feng B, Song Q, Liu SB, Zhao DQ, Zhao MG. Nicotine Addiction Reduces the Large-Conductance Ca2+-activated Potassium Channels Expression in the Nucleus Accumbens. Neuromolecular Med 2012; 15:227-37. [DOI: 10.1007/s12017-012-8213-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 12/07/2012] [Indexed: 11/28/2022]
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Wu X, Shi M, Ling H, Wei C, Liu Y, Liu Z, Ren W. Effects of morphine withdrawal on the membrane properties of medium spiny neurons in the nucleus accumbens shell. Brain Res Bull 2012; 90:92-9. [PMID: 23069789 DOI: 10.1016/j.brainresbull.2012.09.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 09/06/2012] [Accepted: 09/26/2012] [Indexed: 11/17/2022]
Abstract
Medium spiny neurons (MSNs) in the nucleus accumbens (NAc) undergo persistent alterations in their biological and physiological characteristics upon exposure to drugs of abuse. Previous studies demonstrated that the biochemical, morphological, and intrinsic physiological properties of MSNs are heterogeneous and provided new insights into the physiological and molecular roles of individual MSNs in addictive behaviors. However, it remains unclear whether MSNs in the NAc shell (NAcSh), an important region for mediating behavioral sensitization, are electrophysiologically heterogeneous and how such heterogeneity is relevant to neuroadaptation associated with drug addiction. Here, the membrane properties, i.e., the intrinsic excitability and spike adaptation, of MSNs in the NAcSh from saline- or morphine-treated rats were investigated in vitro by whole-cell recording. In saline-treated rats, three distinct cell types were identified by their membrane properties: type I neurons showed high levels of intrinsic excitability and rapid spike adaptation; type II neurons showed moderate levels of intrinsic excitability and relatively slow spike frequency adaptation; type III neurons showed low levels of intrinsic excitability and putative strong spike adaptation. MSNs in rats undergoing withdrawal from chronic morphine treatment (10-14 days after the last injection) also exhibited the typical firing behaviors of these three types of neurons. However, the membrane properties of the MSNs were differentially altered after withdrawal. There was an enhancement in intrinsic excitability in type II MSNs and a promotion of spike adaptation in type I MSNs. The apamin-sensitive afterhyperpolarization current (I(AHP)) and the apamin-insensitive I(AHP) of the NAcSh MSNs were attenuated after chronic morphine withdrawal. These findings suggest that individual MSNs in the NAcSh manifest unique electrophysiological properties, which might contribute to psychostimulant-induced neuroadaptation.
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Affiliation(s)
- Xiaobo Wu
- Key Laboratory of MOE for Modern Teaching Technology, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi 710062, PR China
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18
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AMPAR-independent effect of striatal αCaMKII promotes the sensitization of cocaine reward. J Neurosci 2012; 32:6578-86. [PMID: 22573680 DOI: 10.1523/jneurosci.6391-11.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Changes in CaMKII-regulated synaptic excitability are a means through which experience may modify neuronal function and shape behavior. While behavior in rodent addiction models is linked with CaMKII activity in the nucleus accumbens (NAc) shell, the key cellular adaptations that forge this link are unclear. Using a mouse strain with striatal-specific expression of autonomously active CaMKII (T286D), we demonstrate that while persistent CaMKII activity induces behaviors comparable to those in mice repeatedly exposed to psychostimulants, it is insufficient to increase AMPAR-mediated synaptic strength in NAc shell. However, autonomous CaMKII upregulates A-type K(+) current (IA) and decreases firing in shell neurons. Importantly, inactivating the transgene with doxycycline eliminates both the IA-mediated firing decrease and the elevated behavioral response to cocaine. This study identifies CaMKII regulation of IA in NAc shell neurons as a novel cellular contributor to the sensitization of cocaine reward.
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Wu X, Shi M, Wei C, Yang M, Liu Y, Liu Z, Zhang X, Ren W. Potentiation of synaptic strength and intrinsic excitability in the nucleus accumbens after 10 days of morphine withdrawal. J Neurosci Res 2012; 90:1270-83. [PMID: 22388870 DOI: 10.1002/jnr.23025] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2011] [Revised: 11/29/2011] [Accepted: 12/08/2011] [Indexed: 11/11/2022]
Abstract
Neuroadaptations in the nucleus accumbens (NAc) are associated with the development of drug addiction. Plasticity in synaptic strength and intrinsic excitability of NAc medium spiny neurons (MSNs) play critical roles in addiction induced by different classes of abused drugs. However, it is unknown whether morphine exposure influences synaptic strength, intrinsic excitability or both in NAc. Here we show that chronic withdrawal (10 days after the last injection) from repeated morphine exposure elicited potentiation in both glutamatergic synaptic strength and intrinsic excitability of MSNs in NAc shell (NAcSh). The potentiation of synaptic strength was demonstrated by an increase in the frequency of miniature excitatory postsynaptic currents (mEPSCs), a decrease in the paired-pulse ratio (PPR), and an increase in the ratio of α-amino-3-hydroxy-5-methyl-isoxazole propionic acid receptors (AMPAR)- to N-methyl-D-aspartate receptors (NMDAR)-mediated currents. The potentiation of intrinsic excitability was mediated by inhibition of the sustained potassium currents via extrasynaptic NMDAR activation. The function of the presynaptic group II metabotropic glutamate receptors (mGluR2/3) was downregulated, enhancing the probability of glutamate release on synaptic terminals during chronic morphine withdrawal. Pretreatment with the mGluR2/3 agonist LY379268 completely blocked potentiation of both synaptic strength and intrinsic excitability. These results suggest that chronic morphine withdrawal downregulates mGluR2/3 to induce potentiation of MSN glutamatergic synapse via increased glutamate release, leading to potentiation of intrinsic excitability. Such potentiation of both synaptic strength and intrinsic excitability might contribute to neuroadaptations induced by morphine application.
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Affiliation(s)
- Xiaobo Wu
- Key Laboratory of Modern Teaching Technology and College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, People's Republic of China
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Le Merrer J, Befort K, Gardon O, Filliol D, Darcq E, Dembele D, Becker JAJ, Kieffer BL. Protracted abstinence from distinct drugs of abuse shows regulation of a common gene network. Addict Biol 2012; 17:1-12. [PMID: 21955143 DOI: 10.1111/j.1369-1600.2011.00365.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Addiction is a chronic brain disorder. Prolonged abstinence from drugs of abuse involves dysphoria, high stress responsiveness and craving. The neurobiology of drug abstinence, however, is poorly understood. We previously identified a unique set of hundred mu-opioid receptor-dependent genes in the extended amygdala, a key site for hedonic and stress processing in the brain. Here we examined these candidate genes either immediately after chronic morphine, nicotine, Δ9-tetrahydrocannabinol or alcohol, or following 4 weeks of abstinence. Regulation patterns strongly differed among chronic groups. In contrast, gene regulations strikingly converged in the abstinent groups and revealed unforeseen common adaptations within a novel huntingtin-centered molecular network previously unreported in addiction research. This study demonstrates that, regardless the drug, a specific set of transcriptional regulations develops in the abstinent brain, which possibly contributes to the negative affect characterizing protracted abstinence. This transcriptional signature may represent a hallmark of drug abstinence and a unitary adaptive molecular mechanism in substance abuse disorders.
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Affiliation(s)
- Julie Le Merrer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, INSERM and CNRS, Illkirch-Graffenstaden, France
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Kim J, Park BH, Lee JH, Park SK, Kim JH. Cell type-specific alterations in the nucleus accumbens by repeated exposures to cocaine. Biol Psychiatry 2011; 69:1026-34. [PMID: 21377654 DOI: 10.1016/j.biopsych.2011.01.013] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 12/23/2010] [Accepted: 01/12/2011] [Indexed: 11/29/2022]
Abstract
BACKGROUND The nucleus accumbens (NAc) is a brain region critically involved in psychostimulant-induced neuroadaptations. A major proportion of NAc neurons consists of medium spiny neurons (MSNs), commonly divided into two major subsets on the basis of their expression of D1 dopamine receptors (D1R-MSNs) or D2 dopamine receptors (D2R-MSNs). Although NAc MSNs are known to undergo extensive alterations in their characteristics upon exposure to drugs of abuse, the functional and structural changes specific to each type of MSN have yet to be fully resolved. METHODS We repeatedly injected cocaine into transgenic mice expressing enhanced green fluorescent protein under the control of promoters for either D1R or D2R and then analyzed the physiological characteristics of each type of MSN by whole-cell recording. We also analyzed cocaine-induced changes of spine densities of individual MSNs with recombinant lentivirus in a cell type-specific manner and corroborated findings by use of a pathway-specific labeling using recombinant rabies virus. RESULTS The D1R-MSNs exhibited decreased membrane excitability but increased frequency of miniature excitatory postsynaptic currents after repeated cocaine administration, whereas D2R-MSNs displayed a decrease in miniature excitatory postsynaptic current frequency with no change in excitability. Interestingly, miniature inhibitory postsynaptic currents decreased in D1R-MSNs but were unaffected in D2R-MSNs. Moreover, morphological analyses revealed a selective increase in spine density in D1R-MSNs after chronic cocaine exposure. CONCLUSIONS This study provides the first experimental evidence that NAc MSNs differentially contribute to psychostimulant-induced neuroadaptations by changing their intrinsic, synaptic, and structural characteristics in a cell type-specific fashion.
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Affiliation(s)
- Juhyun Kim
- Department of Life Science, Pohang University of Science and Technology, Pohang, Gyungbuk, Republic of Korea
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22
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Perez MF, Ford KA, Goussakov I, Stutzmann GE, Hu XT. Repeated cocaine exposure decreases dopamine D₂-like receptor modulation of Ca(2+) homeostasis in rat nucleus accumbens neurons. Synapse 2011; 65:168-80. [PMID: 20665696 DOI: 10.1002/syn.20831] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nucleus accumbens (NAc) is a limbic structure in the forebrain that plays a critical role in cognitive function and addiction. Dopamine modulates activity of medium spiny neurons (MSNs) in the NAc. Both dopamine D₁-like and D₂-like receptors (including D1R or D(1,5)R and D2R or D(2,3,4)R, respectively) are thought to play critical roles in cocaine addiction. Our previous studies demonstrated that repeated cocaine exposure (which alters dopamine transmission) decreases excitability of NAc MSNs in cocaine-sensitized, withdrawn rats. This decrease is characterized by a reduction in voltage-sensitive Na(+) currents and high voltage-activated Ca(2+) currents, along with increased voltage-gated K(+) currents. These changes are associated with enhanced activity in the D1R/cAMP/PKA/protein phosphatase 1 pathway and diminished calcineurin function. Although D1R-mediated signaling is enhanced by repeated cocaine exposure, little is known whether and how the D2R is implicated in the cocaine-induced NAc dysfunction. Here, we performed a combined electrophysiological, biochemical, and neuroimaging study that reveals the cocaine-induced dysregulation of Ca(2+) homeostasis with involvement of D2R. Our novel findings reveal that D2R stimulation reduced Ca(2+) influx preferentially via the L-type Ca(2+) channels and evoked intracellular Ca(2+) release, likely via inhibiting the cAMP/PKA cascade, in the NAc MSNs of drug-free rats. However, repeated cocaine exposure abolished the D₂R effects on modulating Ca(2+) homeostasis with enhanced PKA activity and led to a decrease in whole-cell Ca(2+) influx. These adaptations, which persisted for 21 days during cocaine abstinence, may contribute to the mechanism of cocaine withdrawal.
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Affiliation(s)
- Mariela F Perez
- IFEC, CONICET, Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba, Argentina
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23
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Diana M. The dopamine hypothesis of drug addiction and its potential therapeutic value. Front Psychiatry 2011; 2:64. [PMID: 22144966 PMCID: PMC3225760 DOI: 10.3389/fpsyt.2011.00064] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 11/02/2011] [Indexed: 01/28/2023] Open
Abstract
Dopamine (DA) transmission is deeply affected by drugs of abuse, and alterations in DA function are involved in the various phases of drug addiction and potentially exploitable therapeutically. In particular, basic studies have documented a reduction in the electrophysiological activity of DA neurons in alcohol, opiate, cannabinoid, and other drug-dependent rats. Further, DA release in the Nucleus accumbens (Nacc) is decreased in virtually all drug-dependent rodents. In parallel, these studies are supported by increments in intracranial self stimulation (ICSS) thresholds during withdrawal from alcohol, nicotine, opiates, and other drugs of abuse, thereby suggesting a hypofunction of the neural substrate of ICSS. Accordingly, morphological evaluations fed into realistic computational analysis of the medium spiny neuron of the Nacc, post-synaptic counterpart of DA terminals, show profound changes in structure and function of the entire mesolimbic system. In line with these findings, human imaging studies have shown a reduction of dopamine receptors accompanied by a lesser release of endogenous DA in the ventral striatum of cocaine, heroin, and alcohol-dependent subjects, thereby offering visual proof of the "dopamine-impoverished" addicted human brain. The lasting reduction in physiological activity of the DA system leads to the idea that an increment in its activity, to restore pre-drug levels, may yield significant clinical improvements (reduction of craving, relapse, and drug-seeking/taking). In theory, it may be achieved pharmacologically and/or with novel interventions such as transcranial magnetic stimulation (TMS). Its anatomo-physiological rationale as a possible therapeutic aid in alcoholics and other addicts will be described and proposed as a theoretical framework to be subjected to experimental testing in human addicts.
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Affiliation(s)
- Marco Diana
- 'G. Minardi' Cognitive Neuroscience Laboratory, Department of Drug Sciences, University of Sassari Sassari, Italy
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Grant JE, Potenza MN, Weinstein A, Gorelick DA. Introduction to behavioral addictions. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 2010; 36:233-41. [PMID: 20560821 PMCID: PMC3164585 DOI: 10.3109/00952990.2010.491884] [Citation(s) in RCA: 566] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Several behaviors, besides psychoactive substance ingestion, produce short-term reward that may engender persistent behavior, despite knowledge of adverse consequences, i.e., diminished control over the behavior. These disorders have historically been conceptualized in several ways. One view posits these disorders as lying along an impulsive-compulsive spectrum, with some classified as impulse control disorders. An alternate, but not mutually exclusive, conceptualization considers the disorders as non-substance or "behavioral" addictions. OBJECTIVES Inform the discussion on the relationship between psychoactive substance and behavioral addictions. METHODS We review data illustrating similarities and differences between impulse control disorders or behavioral addictions and substance addictions. This topic is particularly relevant to the optimal classification of these disorders in the forthcoming fifth edition of the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders (DSM-V). RESULTS Growing evidence suggests that behavioral addictions resemble substance addictions in many domains, including natural history, phenomenology, tolerance, comorbidity, overlapping genetic contribution, neurobiological mechanisms, and response to treatment, supporting the DSM-V Task Force proposed new category of Addiction and Related Disorders encompassing both substance use disorders and non-substance addictions. Current data suggest that this combined category may be appropriate for pathological gambling and a few other better studied behavioral addictions, e.g., Internet addiction. There is currently insufficient data to justify any classification of other proposed behavioral addictions. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE Proper categorization of behavioral addictions or impulse control disorders has substantial implications for the development of improved prevention and treatment strategies.
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Affiliation(s)
- Jon E. Grant
- University of Minnesota School of Medicine, Minneapolis, Minnesota, USA
| | - Marc N. Potenza
- Yale University School of Medicine, New Haven, Connecticut, USA
| | | | - David A. Gorelick
- Intramural Research Program, National Institute on Drug Abuse, NIH, Baltimore, MD
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Wolf ME. The Bermuda Triangle of cocaine-induced neuroadaptations. Trends Neurosci 2010; 33:391-8. [PMID: 20655604 PMCID: PMC2935206 DOI: 10.1016/j.tins.2010.06.003] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 06/15/2010] [Accepted: 06/15/2010] [Indexed: 01/11/2023]
Abstract
Activation of medium spiny neurons (MSNs) of the nucleus accumbens is critical for goal-directed behaviors including cocaine seeking. Studies in cocaine-experienced rodents have revealed three major categories of neuroadaptations that influence the ability of glutamate inputs to activate MSNs: changes in synaptic AMPA receptor levels, changes in extracellular non-synaptic glutamate levels and changes in MSN intrinsic membrane excitability. Most studies have focused on one of these adaptations. This review will consider the possibility that they are causally related and speculate about how time-dependent changes in their interactions may regulate MSN output during early and late withdrawal from repeated cocaine exposure.
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Affiliation(s)
- Marina E Wolf
- Department of Neuroscience, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064-3095, USA.
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Huang YH, Schlüter OM, Dong Y. Cocaine-induced homeostatic regulation and dysregulation of nucleus accumbens neurons. Behav Brain Res 2010; 216:9-18. [PMID: 20708038 DOI: 10.1016/j.bbr.2010.07.039] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 07/22/2010] [Accepted: 07/30/2010] [Indexed: 12/27/2022]
Abstract
Homeostatic response is an endowed self-correcting/maintaining property for living units, ranging from subcellular domains, single cells, and organs to the whole organism. Homeostatic responses maintain stable function through the ever-changing internal and external environments. In central neurons, several forms of homeostatic regulation have been identified, all of which tend to stabilize the functional output of neurons toward their prior "set-point." Medium spiny neurons (MSNs) within the forebrain region the nucleus accumbens (NAc) play a central role in gating/regulating emotional and motivational behaviors including craving and seeking drugs of abuse. Exposure to highly salient stimuli such as cocaine administration not only acutely activates a certain population of NAc MSNs, but also induces long-lasting changes in these neurons. It is these long-lasting cellular alterations that are speculated to mediate the increasingly strong cocaine-craving and cocaine-seeking behaviors. Why do the potentially powerful homeostatic mechanisms fail to correct or compensate for these drug-induced maladaptations in neurons? Based on recent experimental results, this review proposes a hypothesis of homeostatic dysregulation induced by exposure to cocaine. Specifically, we hypothesize that exposure to cocaine generates false molecular signals which misleads the homeostatic regulation process, resulting in maladaptive changes in NAc MSNs. Thus, many molecular and cellular alterations observed in the addicted brain may indeed result from homeostatic dysregulation. This review is among the first to introduce the concept of homeostatic neuroplasticity to understanding the molecular and cellular maladaptations following exposure to drugs of abuse.
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Affiliation(s)
- Yanhua H Huang
- Program in Neuroscience, Washington State University, Pullman, WA 99164, USA
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AMPA receptor synaptic plasticity induced by psychostimulants: the past, present, and therapeutic future. Neuron 2010; 67:11-24. [PMID: 20624588 DOI: 10.1016/j.neuron.2010.06.004] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2010] [Indexed: 11/20/2022]
Abstract
Experience-dependent plasticity at excitatory synapses of the mesocorticolimbic system is a fundamental brain mechanism that enables adaptation to an ever-changing environment. These synaptic responses are critical for the planning and execution of adaptive behaviors that maximize survival. The mesocorticolimbic system mediates procurement of positive reinforcers such as food and sex; however, drugs of abuse resculpt this crucial circuitry to promote compulsive drug-seeking behavior. This review will discuss the long-term changes in glutamatergic neurotransmission that occur within the mesolimbic system following cocaine exposure. In addition, we will examine how these long-lasting neuroadaptations may drive the pathology of psychostimulant addiction. Finally, we review clinical trials that highlight antagonists at excitatory AMPA receptors as promising targets against cocaine abuse.
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28
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Hu JL, Liu G, Li YC, Gao WJ, Huang YQ. Dopamine D1 receptor-mediated NMDA receptor insertion depends on Fyn but not Src kinase pathway in prefrontal cortical neurons. Mol Brain 2010; 3:20. [PMID: 20569495 PMCID: PMC2902469 DOI: 10.1186/1756-6606-3-20] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 06/22/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Interactions between dopamine and glutamate in the prefrontal cortex are essential for cognitive functions such as working memory. Modulation of N-methyl-D-aspartic acid (NMDA) receptor functions by dopamine D1 receptor is believed to play a critical role in these functions. The aim of the work reported here is to explore the signaling pathway underlying D1 receptor-mediated trafficking of NMDA receptors in cultured rat prefrontal cortical neurons. RESULTS Activation of D1 receptor by selective agonist SKF-81297 significantly increased the expression of NR2B subunits. This effect was completely blocked by small interfering RNA knockdown of Fyn, but not Src. Under control conditions, neither Fyn nor Src knockdown exhibited significant effect on basal NR2B expression. D1 stimulation significantly enhanced NR2B insertion into plasma membrane in cultured PFC neurons, a process obstructed by Fyn, but not Src, knockdown. CONCLUSIONS Dopamine D1 receptor-mediated increase of NMDA receptors is thus Fyn kinase dependent. Targeting this signaling pathway may be useful in treating drug addiction and schizophrenia.
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Affiliation(s)
- Jian-Li Hu
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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29
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Suman A, Mehta B, Guo ML, Chu XP, Fibuch EE, Mao LM, Wang JQ. Alterations in subcellular expression of acid-sensing ion channels in the rat forebrain following chronic amphetamine administration. Neurosci Res 2010; 68:1-8. [PMID: 20566346 DOI: 10.1016/j.neures.2010.06.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 05/27/2010] [Accepted: 06/01/2010] [Indexed: 12/20/2022]
Abstract
Acid-sensing ion channels (ASICs) are densely expressed in broad areas of mammalian brains and actively modulate synaptic transmission and a variety of neuronal activities. To explore whether ASICs are linked to addictive properties of drugs of abuse, we investigated the effect of the psychostimulant amphetamine on subcellular ASIC expression in the rat forebrain in vivo. Repeated administration of amphetamine (once daily for 7 days, 1.25 mg/kg for days 1/7, 4 mg/kg for days 2-6) induced typical behavioral sensitization. At a 14-day withdrawal period, ASIC1 protein levels were increased in the defined surface and intracellular compartments in the striatum (both caudate putamen and nucleus accumbens) in amphetamine-treated rats relative to saline-treated rats as detected by a surface protein cross-linking assay. ASIC2 proteins, however, remained stable in the striatum. In the medial prefrontal cortex, repeated amphetamine administration had no effect on ASIC1 expression in either the surface or the intracellular pool. However, amphetamine selectively reduced the surface expression of ASIC2 in this region. These data identify ASICs as a sensitive target to repeated stimulant exposure. The region- and compartment-specific regulation of ASIC1 and ASIC2 expression may constitute a key synaptic adaptation in reward circuits critical for psychomotor plasticity.
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Affiliation(s)
- Ajay Suman
- Department of Anesthesiology, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA
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Chen BT, Hopf FW, Bonci A. Synaptic plasticity in the mesolimbic system: therapeutic implications for substance abuse. Ann N Y Acad Sci 2010; 1187:129-39. [PMID: 20201850 DOI: 10.1111/j.1749-6632.2009.05154.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In an ever-changing environment, animals must learn new behavioral strategies for the successful procurement of food, sex, and other needs. Synaptic plasticity within the mesolimbic system, a key reward circuit, affords an animal the ability to adapt and perform essential goal-directed behaviors. Ironically, drugs of abuse can also induce synaptic changes within the mesolimbic system, and such changes are hypothesized to promote deleterious drug-seeking behaviors in lieu of healthy, adaptive behaviors. In this review, we will discuss drug-induced neuroadaptations in excitatory transmission in the ventral tegmental area and the nucleus accumbens, two critical regions of the mesolimbic system, and the possible role of dopamine receptors in the development of these neuroadaptations. In particular, we will focus our discussion on recent studies showing changes in AMPA receptor function as a common molecular target of addictive drugs, and the possible behavioral consequences of such neuroadaptations.
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Affiliation(s)
- Billy T Chen
- Ernest Gallo Clinic and Research Center, University of California, San Francisco, California, USA
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31
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Podda MV, Riccardi E, D'Ascenzo M, Azzena GB, Grassi C. Dopamine D1-like receptor activation depolarizes medium spiny neurons of the mouse nucleus accumbens by inhibiting inwardly rectifying K+ currents through a cAMP-dependent protein kinase A-independent mechanism. Neuroscience 2010; 167:678-90. [PMID: 20211700 DOI: 10.1016/j.neuroscience.2010.02.075] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 02/06/2010] [Accepted: 02/28/2010] [Indexed: 01/15/2023]
Abstract
Dopamine/cAMP signaling has been reported to mediate behavioral responses related to drug addiction. It also modulates the plasticity and firing properties of medium spiny neurons (MSNs) in the nucleus accumbens (NAc), although the effects of cAMP signaling on the resting membrane potential (RMP) of MSNs has not been specifically defined. In this study, activation of dopamine D1-like receptors (D1Rs) by SKF-38393 elicited membrane depolarization and inward currents in MSNs from the NAc core of 14-17 day-old mice. Similar results were obtained following stimulation of adenylyl cyclase (AC) activity with forskolin or application of exogenous cAMP. Forskolin occluded SKF-38393's effects, thus indicating that D1R action is mediated by AC/cAMP signaling. Accordingly, AC blockade by SQ22536 significantly inhibited the responses to SKF-38393. Effects elicited by D1R stimulation or increased cAMP levels were unaffected by protein kinase A (PKA) or protein kinase C (PKC) blockade and were not mimicked by the Epac agonist, 8CPT-2Me-cAMP. Responses to forskolin were also not significantly modified by cyclic nucleotide-gated (CNG) channel blockade. Forskolin-induced membrane depolarization was associated with increased membrane input resistance. Voltage-clamp experiments revealed that forskolin and SKF-38393 effects were due to inhibition of resting K(+) currents exhibiting inward rectification at hyperpolarized potentials and a reversal potential (around -90 mV) that shifted with the extracellular K(+) concentration. Forskolin and D1R agonist effects were abolished by the inward rectifier K(+) (Kir)-channel blocker, BaCl(2). Collectively, these data suggest that stimulation of postsynaptic D1Rs in MSNs of the NAc core causes membrane depolarization by inhibiting Kir currents. This effect is mediated by AC/cAMP signaling but it is independent on PKA, PKC, Epac and CNG channel activation, suggesting that it may stem from cAMP's direct interaction with Kir channels. D1R/cAMP-mediated excitatory effects may influence the generation of output signals from MSNs by facilitating their transition from the quiescent down-state to the functionally active up-state.
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Affiliation(s)
- M V Podda
- Institute of Human Physiology, Medical School, Catholic University S. Cuore, Rome, Italy
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Wolf ME, Ferrario CR. AMPA receptor plasticity in the nucleus accumbens after repeated exposure to cocaine. Neurosci Biobehav Rev 2010; 35:185-211. [PMID: 20109488 DOI: 10.1016/j.neubiorev.2010.01.013] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 01/17/2010] [Accepted: 01/20/2010] [Indexed: 10/19/2022]
Abstract
This review focuses on cocaine-induced postsynaptic plasticity in the nucleus accumbens (NAc) involving changes in AMPA receptor (AMPAR) transmission. First, fundamental properties of AMPAR in the NAc are reviewed. Then, we provide a detailed and critical analysis of literature demonstrating alterations in AMPAR transmission in association with behavioral sensitization to cocaine and cocaine self-administration. We conclude that cocaine exposure leads to changes in AMPAR transmission that depend on many factors including whether exposure is contingent or non-contingent, the duration of withdrawal, and whether extinction training has occurred. The relationship between changes in AMPAR transmission and responding to cocaine or cocaine-paired cues can also be affected by these variables. However, after prolonged withdrawal in the absence of extinction training, our findings and others lead us to propose that AMPAR transmission is enhanced, resulting in stronger responding to drug-paired cues. Finally, many results indicate that the state of synaptic transmission in the NAc after cocaine exposure is associated with impairment of AMPAR-dependent plasticity. This may contribute to a broad range of addiction-related behavioral changes.
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Affiliation(s)
- Marina E Wolf
- Department of Neuroscience, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064-3095, United States.
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Guillem K, Kravitz AV, Moorman DE, Peoples LL. Orbitofrontal and insular cortex: neural responses to cocaine-associated cues and cocaine self-administration. Synapse 2010; 64:1-13. [PMID: 19725114 DOI: 10.1002/syn.20698] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Based on neuro-imaging studies in cocaine-addicted humans, it is hypothesized that increases in neural activity within several regions of the prefrontal cortex contribute to cue-induced cocaine seeking and cocaine-induced compulsive drug self-administration. However, electrophysiological tests of these hypotheses are lacking. In the present study, animals were trained to self-administer cocaine (0.75 mg/kg) for 14 days. On the 14th day, we conducted electrophysiological recordings of lateral orbitofrontal (LO) and ventral anterior insula (AIV) neurons. A subset of the combined population of recorded neurons showed a change in firing rate in association with one or more of the following discrete events: (1) presentation of a discriminative stimulus that signaled the onset of the self-administration session, (2) occurrence of the first cocaine-directed operant response, (3) occurrence of a cocaine-reinforced press, and (4) presentation of cues normally paired with delivery of the cocaine reinforcer. The majority of the stimulus- and response-related changes in firing involved a brief increase in firing during the stimulus and response event, respectively. In addition to these event-specific responses, approximately half of the recorded neurons exhibited a sustained change in average firing (i.e., discharges per 30-s bin) during the cocaine self-administration session, relative to average firing during a presession, drug-free period (referred to as session changes). The prevalence of session-increases and decreases were not significantly different. These and other findings are discussed in relation to hypotheses about cue-evoked and cocaine-maintained cocaine-directed behavior.
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Affiliation(s)
- Karine Guillem
- Department of Psychiatry, TRL, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Similar neurons, opposite adaptations: psychostimulant experience differentially alters firing properties in accumbens core versus shell. J Neurosci 2009; 29:12275-83. [PMID: 19793986 DOI: 10.1523/jneurosci.3028-09.2009] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The principal components of neuronal excitability include synaptic and intrinsic membrane parameters. While recent studies indicate that cocaine exposure can induce widespread changes in synaptic function in the neural circuits for reward, intrinsic firing properties have received much less attention. Using whole-cell recording in ex vivo brain slices from cocaine-treated mice, we studied the intrinsic firing characteristics of medium-spiny projection neurons of the nucleus accumbens--a key node in the circuit that controls reward-directed behavior. Our data demonstrate that repeated in vivo cocaine (5 x 15 mg/kg, i.p., once daily, 5 d) induces opposite changes in neurons of the two main subdivisions of the accumbens, the shell and the core. While shell neurons exhibit an initial depression in firing capacity (1-3 d abstinence) that persists for at least 2 weeks, core neurons exhibit increased firing capacity during early abstinence (1-3 d) that declines to basal levels within 2 weeks. Shared adaptations between addictive drugs may mediate core processes of addiction. We find that amphetamine exposure (5 x 5 mg/kg, i.p., once daily, 5 d) that induced a similar degree of locomotor sensitization as cocaine also induced an indistinguishable pattern of NAc intrinsic plasticity. Finally, we provided evidence that opposite regulation of A-type potassium current is an important factor in this bidirectional intrinsic plasticity for both cocaine and amphetamine. We propose that a persistent disparity in core/shell excitability might be an important mediator of the changes in reward circuit activity that drive drug-seeking behavior in animal models of addiction.
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Nair SG, Adams-Deutsch T, Epstein DH, Shaham Y. The neuropharmacology of relapse to food seeking: methodology, main findings, and comparison with relapse to drug seeking. Prog Neurobiol 2009; 89:18-45. [PMID: 19497349 PMCID: PMC2745723 DOI: 10.1016/j.pneurobio.2009.05.003] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 04/09/2009] [Accepted: 05/26/2009] [Indexed: 12/15/2022]
Abstract
Relapse to old, unhealthy eating habits is a major problem in human dietary treatments. The mechanisms underlying this relapse are unknown. Surprisingly, until recently this clinical problem has not been systematically studied in animal models. Here, we review results from recent studies in which a reinstatement model (commonly used to study relapse to abused drugs) was employed to characterize the effect of pharmacological agents on relapse to food seeking induced by either food priming (non-contingent exposure to small amounts of food), cues previously associated with food, or injections of the pharmacological stressor yohimbine. We also address methodological issues related to the use of the reinstatement model to study relapse to food seeking, similarities and differences in mechanisms underlying reinstatement of food seeking versus drug seeking, and the degree to which the reinstatement procedure provides a suitable model for studying relapse in humans. We conclude by discussing implications for medication development and future research. We offer three tentative conclusions: (1)The neuronal mechanisms of food-priming- and cue-induced reinstatement are likely different from those of reinstatement induced by the pharmacological stressor yohimbine. (2)The neuronal mechanisms of reinstatement of food seeking are possibly different from those of ongoing food-reinforced operant responding. (3)The neuronal mechanisms underlying reinstatement of food seeking overlap to some degree with those of reinstatement of drug seeking.
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Affiliation(s)
- Sunila G. Nair
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - Tristan Adams-Deutsch
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - David H. Epstein
- Clinical Pharmacology and Therapeutics Research Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
| | - Yavin Shaham
- Behavioral Neuroscience Branch, NIDA/IRP, 251 Bayview Boulevard, Baltimore, MD, 21224
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Abstract
Increased reactivity of certain frontal cortical brain regions to cocaine re-exposure or drug-associated cues in cocaine-abstinent human addicts is linked to drug craving. Similarly, in rats tested after withdrawal from repeated cocaine exposure, cocaine or other strong excitatory stimuli produce greater activation of pyramidal neurons in the medial prefrontal cortex (mPFC). Our recent findings indicate that the increased mPFC neuronal activation depends primarily upon enhanced voltage-sensitive Ca(2+) influx, most likely through high-voltage activated (HVA) L-type Ca(2+) channels, but the mechanism underlying the enhanced Ca(2+) currents is unknown. In this study, we used a protein crosslinking assay to show that repeated cocaine injections, resulting in behavioral sensitization, increased total protein levels and cell surface expression of HVA-Ca(v)1.2 L-type channels in pyramidal neurons in deep layers of the mPFC. These changes in Ca(v)1.2 L-channels were time dependent and subtype specific (i.e., differed from those observed for Ca(v)1.3 L-channels). Furthermore, we found enhanced PKA activity in the mPFC of cocaine-sensitized rats that persisted for 21 days after withdrawal. PKA phosphorylation of L-channels increases their activity, so Ca(2+) currents after cocaine withdrawal could be enhanced as a result of both increased activity and number of HVA-Ca(v)1.2 L-channels on the cell surface. By increasing the suprafiring threshold excitability of mPFC pyramidal neurons, excessive upregulation of HVA L-channel activity and number may contribute to the cortical hyper-responsiveness that enhances vulnerability to cocaine craving and relapse. More generally, our results are the first to demonstrate that repeated cocaine exposure alters the membrane trafficking of a voltage-sensitive ion channel.
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Affiliation(s)
- Kerstin A Ford
- Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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Parelkar NK, Jiang Q, Chu XP, Guo ML, Mao LM, Wang JQ. Amphetamine alters Ras-guanine nucleotide-releasing factor expression in the rat striatum in vivo. Eur J Pharmacol 2009; 619:50-6. [PMID: 19686726 DOI: 10.1016/j.ejphar.2009.08.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 07/14/2009] [Accepted: 08/03/2009] [Indexed: 01/30/2023]
Abstract
Ras-guanine nucleotide-releasing factors (Ras-GRFs) are densely expressed in neurons of the mammalian brain. As a Ras-specific activator predominantly concentrated at synaptic sites, Ras-GRFs activate the Ras-mitogen-activated protein kinase (Ras-MAPK) cascade in response to changing synaptic inputs, thereby modifying a variety of cellular and synaptic activities. While the Ras-MAPK cascade in the limbic reward circuit is well-known to be sensitive to dopamine inputs, the sensitivity of its upstream activator (Ras-GRFs) to dopamine remains to be investigated. In this study, the response of Ras-GRFs in their protein expression to dopamine stimulation was evaluated in the rat striatum in vivo. A single systemic injection of the psychostimulant amphetamine produced an increase in Ras-GRF1 protein levels in both the dorsal (caudoputamen) and ventral (nucleus accumbens) striatum. The increase in Ras-GRF1 proteins was dose-dependent. The reliable increase was seen 2.5h after drug injection and returned to normal levels by 6h. In contrast to Ras-GRF1, protein levels of Ras-GRF2 in the striatum were not altered by amphetamine. In addition to the striatum, the medial prefrontal cortex is another forebrain site where amphetamine induced a parallel increase in Ras-GRF1 but not Ras-GRF2. No significant change in Ras-GRF1/2 proteins was observed in the hippocampus. These data demonstrate that Ras-GRF1 is a susceptible and selective target of amphetamine in striatal and cortical neurons. Its protein expression is subject to the modulation by acute exposure of amphetamine.
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Affiliation(s)
- Nikhil K Parelkar
- Department of Pharmacology, School of Pharmacy, University of Missouri-Kansas City, 2411 Holmes Street, Kansas City, Missouri 64108, USA
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38
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Sun X, Wolf ME. Nucleus accumbens neurons exhibit synaptic scaling that is occluded by repeated dopamine pre-exposure. Eur J Neurosci 2009; 30:539-50. [PMID: 19674091 DOI: 10.1111/j.1460-9568.2009.06852.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synaptic scaling has been proposed as a form of plasticity that may contribute to drug addiction but it has not been previously demonstrated in the nucleus accumbens (NAc), a critical region for addiction. Here we demonstrate bidirectional synaptic scaling in postnatal rat NAc neurons that were co-cultured with prefrontal cortical neurons to restore excitatory input. Prolonged activity blockade (1-3 days) with an AMPA receptor antagonist increased cell surface (synaptic and extrasynaptic) glutamate receptor 1 (GluR1) and GluR2 but not GluR3, as well as GluR1/2 co-localization on the cell surface and total GluR1 and GluR2 protein levels. A prolonged increase in activity (bicuculline, 48 h) produced opposite effects. These results suggest that GluR1/2-containing AMPA receptors undergo synaptic scaling in NAc neurons. GluR1 and GluR2 surface expression was also increased by tetrodotoxin alone or in combination with an N-methyl-d-aspartate receptor or AMPA receptor antagonist but not by the l-type Ca(2+) channel antagonist nifedipine. A cobalt-quenching assay confirmed the immunocytochemical results indicating that synaptic scaling after activity blockade did not involve a change in abundance of GluR2-lacking AMPA receptors. Increased AMPA receptor surface expression after activity blockade required protein synthesis and was occluded by inhibition of the ubiquitin-proteasome system. Repeated dopamine (DA) treatment, which leads to upregulation of surface GluR1 and GluR2, occluded activity blockade-induced synaptic scaling. These latter results indicate an interaction between cellular mechanisms involved in synaptic scaling and adaptive mechanisms triggered by repeated DA receptor stimulation, suggesting that synaptic scaling may not function normally after exposure to DA-releasing drugs such as cocaine.
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Affiliation(s)
- Xiu Sun
- Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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39
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Abstract
Addiction is associated with neuroplasticity in the corticostriatal brain circuitry that is important for guiding adaptive behaviour. The hierarchy of corticostriatal information processing that normally permits the prefrontal cortex to regulate reinforcement-seeking behaviours is impaired by chronic drug use. A failure of the prefrontal cortex to control drug-seeking behaviours can be linked to an enduring imbalance between synaptic and non-synaptic glutamate, termed glutamate homeostasis. The imbalance in glutamate homeostasis engenders changes in neuroplasticity that impair communication between the prefrontal cortex and the nucleus accumbens. Some of these pathological changes are amenable to new glutamate- and neuroplasticity-based pharmacotherapies for treating addiction.
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40
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Abstract
The development of drug addiction progresses along a continuum from acute drug use to compulsive use and drug seeking behavior. Many researchers have focused on identifying the physiological mechanisms involved in drug addiction in order to develop effective pharmacotherapies. Neuroplasticity, the putative mechanism underlying learning and memory, is modified by drugs of abuse and may contribute to the development of the eventual addicted state. Innovative treatments directly targeting these drug-induced changes in brain reward components and circuits may be efficacious in reducing drug use and relapse.
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Affiliation(s)
- Jason L. Niehaus
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island
| | - Nelson D. Cruz-Bermúdez
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island
| | - Julie A. Kauer
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island
- Department of Neuroscience, Brown University, Providence, Rhode Island
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41
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Zhang GC, Mao LM, Wang JQ, Chu XP. Upregulation of acid-sensing ion channel 1 protein expression by chronic administration of cocaine in the mouse striatum in vivo. Neurosci Lett 2009; 459:119-22. [PMID: 19427358 DOI: 10.1016/j.neulet.2009.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 05/04/2009] [Accepted: 05/05/2009] [Indexed: 10/20/2022]
Abstract
Acid-sensing ion channels (ASICs) are ligand-gated cation channels activated by a drop in extracellular pH. They are enriched in the mammalian brain with a high synaptic density. Accumulating evidence suggests that ASIC1 contributes to synaptic activity related to learning/memory and fear conditioning, and also plays critical roles in neurodegenerative diseases. In this study, we explored the effect of the psychostimulant, cocaine, on protein expression of ASICs in the mouse forebrain in vivo. We found that chronic systemic injection of cocaine (20mg/kg, once daily for 5 consecutive days; 14 days of withdrawal) increased ASIC1, but not ASIC2, protein levels in the striatum, including the dorsal (caudate putamen) and the ventral (nucleus accumbens) striatum. No significant changes in ASIC1 or 2 protein levels in the median prefrontal cortex and the hippocampus were observed following the chronic cocaine administration. These data demonstrate that chronic cocaine exposure can upregulate ASIC expression in the striatum in a subunit-selective manner.
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Affiliation(s)
- Guo-Chi Zhang
- Department of Basic Medical Science, University of Missouri-Kansas City School of Medicine, 2411 Holmes Street, Kansas City, MO 64108, USA
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42
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Stability of surface NMDA receptors controls synaptic and behavioral adaptations to amphetamine. Nat Neurosci 2009; 12:602-10. [PMID: 19349975 PMCID: PMC2749993 DOI: 10.1038/nn.2300] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Accepted: 02/19/2009] [Indexed: 01/30/2023]
Abstract
Plastic changes in glutamatergic synapses that lead to enduring drug craving and addiction are poorly understood. By focusing on the turnover and trafficking of NMDA receptors, we found that chronic exposure to the psychostimulant amphetamine induces selective downregulation of NMDA receptor NR2B subunits in the confined surface membrane pool of rat striatal neurons at synaptic sites. Remarkably, this downregulation is a long-lived event and results from the destabilization of surface-expressed NR2B due to accelerated ubiquitination and degradation of crucial NR2B-anchoring proteins by the ubiquitin-proteasome system. The biochemical loss of synaptic NR2B further translates to the significant modulation of synaptic plasticity in the form of long-term depression at cortico-accumbal glutamatergic synapses. Behaviorally, genetic disruption of NR2B induces, whereas restoration of NR2B loss prevents, behavioral sensitization to amphetamine. Our data identify NR2B as a key regulator in the remodeling of excitatory synapses and persistent psychomotor plasticity in response to amphetamine.
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43
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McGinty VB, Grace AA. Timing-dependent regulation of evoked spiking in nucleus accumbens neurons by integration of limbic and prefrontal cortical inputs. J Neurophysiol 2009; 101:1823-35. [PMID: 19193767 DOI: 10.1152/jn.91162.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Single nucleus accumbens (NAcc) neurons receive excitatory synaptic input from cortical and limbic structures, and the integration of converging goal- and motivation-related signals in these neurons influences reward-directed actions. While limbic/cortical synaptic input summation has been characterized at subthreshold intensities, the manner in which multiple inputs govern NAcc neuron spike discharge has not been measured and is poorly understood. Single NAcc neurons were recorded in urethane-anesthetized rats, and spiking was evoked by coincident stimulation of two major NAcc afferent regions: the basolateral amygdala (BLA) and medial prefrontal cortex (mPFC). BLA input increased NAcc spiking elicited by mPFC stimulation depending on the timing of the stimulation pulses, consistent with the summation of monosynaptically evoked excitatory activity. When mPFC input intensity was below threshold for evoked spiking, the addition of BLA input produced the largest facilitation of evoked spiking, and the latency of the evoked spikes reflected the latency of the individual inputs. When mPFC inputs were stimulated at higher intensities, BLA-mediated facilitation was weaker, and the spike latency reflected only the mPFC input. Thus NAcc neurons integrate both the magnitude and timing of afferent synaptic activity, suggesting that NAcc neuron output is strongly dependent on the comparative magnitude of synaptic activity in its afferent structures. These interactions may be crucial integrative mechanisms that allow motivational and cognitive information to produce appropriate reward-directed actions.
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Affiliation(s)
- Vincent B McGinty
- Dept. of Neuroscience, A210 Langley Hall, University of Pittsburgh, Pittsburgh, PA 15260. )
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44
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Bachtell RK, Self DW. Renewed cocaine exposure produces transient alterations in nucleus accumbens AMPA receptor-mediated behavior. J Neurosci 2008; 28:12808-14. [PMID: 19036973 PMCID: PMC2615571 DOI: 10.1523/jneurosci.2060-08.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Revised: 10/08/2008] [Accepted: 10/17/2008] [Indexed: 11/21/2022] Open
Abstract
Withdrawal from repeated cocaine is associated with increased synaptic and extrasynaptic AMPA receptor (AMPAR) expression in nucleus accumbens (NAc) neurons and enhanced behavioral sensitivity to AMPAR stimulation. Recent studies found that increased membrane expression of AMPARs is reversed or normalized on cocaine reexposure in withdrawal, but the mechanism for this AMPAR plasticity and the behavioral implications are unknown. Here, we examine the effects of renewed cocaine exposure during withdrawal on enhanced NAc AMPAR sensitivity and investigate the underlying mechanisms. Cocaine reexposure transiently reversed enhanced NAc AMPAR-mediated locomotion 1 d later, while enhancing cocaine-induced locomotion. Reversal in AMPAR sensitivity was prohibited by NAc AMPAR blockade with CNQX during cocaine reexposure and mimicked by intra-NAc infusions of AMPA, suggesting that cocaine-induced glutamate stimulation of NAc AMPARs is necessary for reversing AMPAR responsiveness. Similarly, systemic treatment with the dopamine D(1)-like agonist SKF 81297 [(+/-)-6-chloro-7,8-dihydroxy-l-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide] reversed AMPAR responsiveness in cocaine withdrawal, but the effect was prevented by local NAc AMPAR blockade in the NAc, and not local D(1)-like receptor blockade, suggesting a role for glutamate afferents in the reversal of enhanced AMPAR sensitivity. Together, these findings suggest that cocaine-induced glutamate release in sensitized animals is responsible for dynamic alterations in AMPAR function that contribute to enhanced cocaine sensitivity.
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Affiliation(s)
- Ryan K Bachtell
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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45
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Gerdeman GL, Schechter JB, French ED. Context-specific reversal of cocaine sensitization by the CB1 cannabinoid receptor antagonist rimonabant. Neuropsychopharmacology 2008; 33:2747-59. [PMID: 18059436 DOI: 10.1038/sj.npp.1301648] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The CB(1) cannabinoid receptor is implicated in the rewarding properties of many drugs of abuse, including cocaine. While CB(1) receptor involvement in the acute rewarding properties of cocaine is controversial, CB(1) antagonists such as SR141716 (rimonabant) have clearly been found to prevent cue- and cocaine-elicited reinstatement of cocaine self-administration in rodents. Here we demonstrate the novel involvement of CB(1) receptors in the maintenance of behavioral sensitization to cocaine in C57BL/6 mice. Consistent with previous reports, the induction of locomotor sensitization following repeated daily cocaine was not prevented by systemic pretreatment of either rimonabant, Delta(9)-tetrahydrocannabinol (THC), or a 1:1 mixture of THC and cannabidiol (CBD). In contrast, established cocaine sensitization was markedly disrupted following subchronic treatment with rimonabant alone. This effect was notably context-dependent, in that rimonabant did not diminish established cocaine sensitization if delivered in the home cage, but only if the rimonabant-injected mice were exposed to activity chambers previously paired with cocaine. These findings are consistent with CB(1) receptor involvement in conditioned cocaine-seeking behaviors, and further suggest that endocannabinoid (eCB)-mediated synaptic plasticity may act specifically within drug-paired environments to maintain cocaine-directed behavioral responses.
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Affiliation(s)
- Gregory L Gerdeman
- Department of Pharmacology, University of Arizona Health Sciences Center, Tucson, AZ 85724-5050, USA.
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46
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Befort K, Filliol D, Ghate A, Darcq E, Matifas A, Muller J, Lardenois A, Thibault C, Dembele D, Le Merrer J, Becker JAJ, Poch O, Kieffer BL. Mu-opioid receptor activation induces transcriptional plasticity in the central extended amygdala. Eur J Neurosci 2008; 27:2973-84. [PMID: 18588537 DOI: 10.1111/j.1460-9568.2008.06273.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Addiction develops from the gradual adaptation of the brain to chronic drug exposure, and involves genetic reprogramming of neuronal function. The central extended amygdala (EAc) is a network formed by the central amygdala and the bed nucleus of the stria terminalis. This key site controls drug craving and seeking behaviors, and has not been investigated at the gene regulation level. We used Affymetrix microarrays to analyze transcriptional activity in the murine EAc, with a focus on mu-opioid receptor-associated events because these receptors mediate drug reward and dependence. We identified 132 genes whose expression is regulated by a chronic escalating morphine regimen in the EAc from wild-type but not mu-opioid receptor knockout mice. These modifications are mostly EAc-specific. Gene ontology analysis reveals an overrepresentation of neurogenesis, cell growth and signaling protein categories. A separate quantitative PCR analysis of genes in the last of these groups confirms the dysregulation of both orphan (Gpr88) and known (DrD1A, Adora2A, Cnr1, Grm5, Gpr6) G protein-coupled receptors, scaffolding (PSD95, Homer1) and signaling (Sgk, Cap1) proteins, and neuropeptides (CCK, galanin). These transcriptional modifications do not occur following a single morphine injection, and hence result from long-term adaptation to excessive mu receptor activation. Proteins encoded by these genes are classically associated with spine modules function in other brain areas, and therefore our data suggest a remodeling of EAc circuits at sites where glutamatergic and monoaminergic afferences interact. Together, mu receptor-dependent genes identified in this study potentially contribute to drug-induced neural plasticity, and provide a unique molecular repertoire towards understanding drug craving and relapse.
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Affiliation(s)
- K Befort
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Département Neurobiologie et Génétique, Illkirch, F-67400 France.
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47
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Kalivas PW, Lalumiere RT, Knackstedt L, Shen H. Glutamate transmission in addiction. Neuropharmacology 2008; 56 Suppl 1:169-73. [PMID: 18675832 DOI: 10.1016/j.neuropharm.2008.07.011] [Citation(s) in RCA: 258] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2008] [Revised: 07/05/2008] [Accepted: 07/08/2008] [Indexed: 01/06/2023]
Abstract
Cortico-striatal glutamate transmission has been implicated in both the initiation and expression of addiction related behaviors, such as locomotor sensitization and drug-seeking. While glutamate transmission onto dopamine cells in the ventral tegmental area undergoes transient plasticity important for establishing addiction-related behaviors, glutamatergic plasticity in the nucleus accumbens is critical for the expression of these behaviors. This information points to the value of exploring pharmacotherapeutic manipulation of glutamate plasticity in treating drug addiction.
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Affiliation(s)
- Peter W Kalivas
- Department of Neurosciences, 173 Ashley Ave, BSB410, Medical University of South Carolina, Charleston, SC 29464, USA.
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Wheeler RA, Carelli RM. Dissecting motivational circuitry to understand substance abuse. Neuropharmacology 2008; 56 Suppl 1:149-59. [PMID: 18625253 DOI: 10.1016/j.neuropharm.2008.06.028] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Revised: 06/09/2008] [Accepted: 06/16/2008] [Indexed: 11/17/2022]
Abstract
An important goal of cocaine addiction research is to understand the neurobiological mechanisms underlying this disease state. Here, we review studies from our laboratory that examined nucleus accumbens (NAc) cell firing and rapid dopamine signaling using electrophysiological and electrochemical recordings in behaving rodents. A major advantage of these techniques is that they allow for the characterization of NAc activity and rapid dopamine release during specific phases of motivated behavior. Moreover, each approach enables an examination of the dynamic nature of NAc signaling as a function of factors such as hedonics and associative learning. We show that NAc neurons differentially respond to rewarding and aversive stimuli and their predictors in a bivalent manner. This differential responding is modifiable and can be altered by the presentation of other natural rewards or cocaine. Likewise, the dynamic nature of NAc cell firing is also reflected in the differential activation of distinct populations of NAc neurons during goal-directed behaviors for natural versus drug rewards, and the heightened activation of some NAc neurons following cocaine abstinence. Our electrochemical data also show that rapid dopamine signaling in the NAc reflects primary rewards and their predictors and appears to modulate specific NAc neuronal responses. In some cases, these influences are observed in a regionally specific manner that matches previous pharmacological manipulations. Collectively, these findings provide critical insight into the functional organization of the NAc that can be used to guide additional studies aimed at dissecting the neural code underlying compulsive drug-seeking behavior.
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Affiliation(s)
- Robert A Wheeler
- Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Bachtell RK, Choi KH, Simmons DL, Falcon E, Monteggia LM, Neve RL, Self DW. Role of GluR1 expression in nucleus accumbens neurons in cocaine sensitization and cocaine-seeking behavior. Eur J Neurosci 2008; 27:2229-40. [PMID: 18430032 DOI: 10.1111/j.1460-9568.2008.06199.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chronic cocaine use reduces glutamate levels in the nucleus accumbens (NAc), and is associated with experience-dependent changes in (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) glutamate receptor membrane expression in NAc neurons. These changes accompany behavioral sensitization to cocaine and increased susceptibility to cocaine relapse. The functional relationship between neuroplasticity in AMPA receptors and the behavioral manifestation of cocaine addiction remains unclear. Thus, we examined the behavioral effects of up- and downregulating basal AMPA receptor function in the NAc core and shell using viral-mediated gene transfer of wild-type glutamate receptor 1 (wt-GluR1) or a dominant-negative pore-dead GluR1 (pd-GluR1), respectively. Transient increases in wt-GluR1 during or after cocaine treatments diminished the development of cocaine sensitization, while pd-GluR1 expression exacerbated cocaine sensitization. Parallel changes were found in D2, but not D1, receptor-mediated behavioral responses. As a correlate of the sensitization experiments, we overexpressed wt- or pd-GluR1 in the NAc core during cocaine self-administration, and tested the effects on subsequent drug-seeking behavior 3 weeks after overexpression declined. wt-GluR1 overexpression during self-administration had no effect on cocaine intake, but subsequently reduced cocaine seeking in extinction and cocaine-induced reinstatement, whereas pd-GluR1 facilitated cocaine-induced reinstatement. When overexpressed during reinstatement tests, wt-GluR1 directly attenuated cocaine- and D2 agonist-induced reinstatement, while pd-GluR1 enhanced reinstatement. In both experimental procedures, neither wt- nor pd-GluR1 expression affected cue-induced reinstatement. Together, these results suggest that degrading basal AMPA receptor function in NAc neurons is sufficient to facilitate relapse via sensitization in D2 receptor responses, whereas elevating basal AMPA receptor function attenuates these behaviors.
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Affiliation(s)
- Ryan K Bachtell
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Kalivas PW. Cocaine and amphetamine-like psychostimulants: neurocircuitry and glutamate neuroplasticity. DIALOGUES IN CLINICAL NEUROSCIENCE 2008. [PMID: 18286799 PMCID: PMC3202508 DOI: 10.31887/dcns.2007.9.4/pkalivas] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Although the pharmacology of amphetamine-like psychostimulants at dopamine transporters is well understood, addiction to this class of drugs has proven difficult to deal with. The reason for this disconnection is that while the molecular mechanism of amphetamine action is critical to reinforce drug use, it is only the first step in a sequence of widespread neuroplastic events in brain circuitry. This review outlines the affect of psychostimulants on mesocorticolimbic dopamine projections that mediate their reinforcing effect, and how this action ultimately leads to enduring pathological neuroplasticity in glutamatergic projections from the prefrontal cortex to the nucleus accumbens. Molecular neuroadaptations induced by psychostimulant abuse are described in glutamate neurotransmission, and from this information potential pharmacotherapeutic targets are identified, based upon reversing or countermanding psychostimulant-induced neuroplasticity.
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Affiliation(s)
- Peter W Kalivas
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA.
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