1
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Fox ME, Wulff AB, Franco D, Choi EY, Calarco CA, Engeln M, Turner MD, Chandra R, Rhodes VM, Thompson SM, Ament SA, Lobo MK. Adaptations in Nucleus Accumbens Neuron Subtypes Mediate Negative Affective Behaviors in Fentanyl Abstinence. Biol Psychiatry 2023; 93:489-501. [PMID: 36435669 PMCID: PMC9931633 DOI: 10.1016/j.biopsych.2022.08.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/25/2022] [Accepted: 08/24/2022] [Indexed: 01/18/2023]
Abstract
BACKGROUND Opioid discontinuation generates a withdrawal syndrome marked by increased negative affect. Increased symptoms of anxiety and dysphoria during opioid discontinuation are significant barriers to achieving long-term abstinence in opioid-dependent individuals. While adaptations in the nucleus accumbens are implicated in opioid abstinence syndrome, the precise neural mechanisms are poorly understood. Additionally, our current knowledge is limited to changes following natural and semisynthetic opioids, despite recent increases in synthetic opioid use and overdose. METHODS We used a combination of cell subtype-specific viral labeling and electrophysiology in male and female mice to investigate structural and functional plasticity in nucleus accumbens medium spiny neuron (MSN) subtypes after fentanyl abstinence. We characterized molecular adaptations after fentanyl abstinence with subtype-specific RNA sequencing and weighted gene co-expression network analysis. We used viral-mediated gene transfer to manipulate the molecular signature of fentanyl abstinence in D1-MSNs. RESULTS Here, we show that fentanyl abstinence increases anxiety-like behavior, decreases social interaction, and engenders MSN subtype-specific plasticity in both sexes. D1-MSNs, but not D2-MSNs, exhibit dendritic atrophy and an increase in excitatory drive. We identified a cluster of coexpressed dendritic morphology genes downregulated selectively in D1-MSNs that are transcriptionally coregulated by E2F1. E2f1 expression in D1-MSNs protects against loss of dendritic complexity, altered physiology, and negative affect-like behaviors caused by fentanyl abstinence. CONCLUSIONS Our findings indicate that fentanyl abstinence causes unique structural, functional, and molecular changes in nucleus accumbens D1-MSNs that can be targeted to alleviate negative affective symptoms during abstinence.
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Affiliation(s)
- Megan E Fox
- Departments of Anesthesiology and Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania; Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland.
| | - Andreas B Wulff
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Daniela Franco
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Eric Y Choi
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Cali A Calarco
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Michel Engeln
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Makeda D Turner
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Ramesh Chandra
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Victoria M Rhodes
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Scott M Thompson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland
| | - Seth A Ament
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland; Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland
| | - Mary Kay Lobo
- Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland.
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Flook EA, Luchsinger JR, Silveri MM, Winder DG, Benningfield MM, Blackford JU. Anxiety during abstinence from alcohol: A systematic review of rodent and human evidence for the anterior insula's role in the abstinence network. Addict Biol 2021; 26:e12861. [PMID: 31991531 DOI: 10.1111/adb.12861] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 11/13/2019] [Accepted: 11/23/2019] [Indexed: 12/30/2022]
Abstract
Alcohol Use Disorder (AUD) is a chronic, relapsing disease that impacts almost a third of Americans. Despite effective treatments for attaining sobriety, the majority of patients relapse within a year, making relapse a substantial barrier to long-term treatment success. A major factor contributing to relapse is heightened negative affect that results from the combination of abstinence-related increases in stress-reactivity and decreases in reward sensitivity. Substantial research has contributed to the understanding of reward-related changes in AUD. However, less is known about anxiety during abstinence, a critical component of understanding addiction as anxiety during abstinence can trigger relapse. Most of what we know about abstinence-related negative affect comes from rodent studies which have identified key brain regions responsible for abstinence-related behaviors. This abstinence network is composed of brain regions that make up the extended amygdala: the nucleus accumbens (NAcc), the central nucleus of the amygdala (CeA), and the bed nucleus of the stria terminalis (BNST). More recently, emerging evidence from rodent and human studies suggests a fourth brain region, the anterior insula, might be part of the abstinence network. Here, we review current rodent and human literature on the extended amygdala's role in alcohol abstinence and anxiety, present evidence for the anterior insula's role in the abstinence network, and provide future directions for research to further elucidate the neural underpinnings of abstinence in humans. A better understanding of the abstinence network is critical toward understanding and possibly preventing relapse in AUD.
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Affiliation(s)
- Elizabeth A. Flook
- Vanderbilt Center for Addiction Research Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt Brain Institute Vanderbilt University School of Medicine Nashville TN USA
- Department of Psychiatry and Behavioral Sciences Vanderbilt University Medical Center Nashville TN USA
| | - Joseph R. Luchsinger
- Vanderbilt Center for Addiction Research Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt Brain Institute Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt J.F. Kennedy Center for Research on Human Development Vanderbilt University School of Medicine Nashville TN USA
| | - Marisa M. Silveri
- Neurodevelopmental Laboratory on Addictions and Mental Health, Brain Imaging Center, McLean Hospital Belmont MA USA
- Department of Psychiatry Harvard Medical School Boston MA USA
| | - Danny G. Winder
- Vanderbilt Center for Addiction Research Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt Brain Institute Vanderbilt University School of Medicine Nashville TN USA
- Department of Psychiatry and Behavioral Sciences Vanderbilt University Medical Center Nashville TN USA
- Vanderbilt J.F. Kennedy Center for Research on Human Development Vanderbilt University School of Medicine Nashville TN USA
- Department of Molecular Physiology and Biophysics Vanderbilt University School of Medicine Nashville TN USA
| | - Margaret M. Benningfield
- Vanderbilt Center for Addiction Research Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt Brain Institute Vanderbilt University School of Medicine Nashville TN USA
- Department of Psychiatry and Behavioral Sciences Vanderbilt University Medical Center Nashville TN USA
| | - Jennifer Urbano Blackford
- Vanderbilt Center for Addiction Research Vanderbilt University School of Medicine Nashville TN USA
- Vanderbilt Brain Institute Vanderbilt University School of Medicine Nashville TN USA
- Department of Psychiatry and Behavioral Sciences Vanderbilt University Medical Center Nashville TN USA
- Vanderbilt J.F. Kennedy Center for Research on Human Development Vanderbilt University School of Medicine Nashville TN USA
- Research Health Scientist, Research and Development, Department of Veterans Affairs Medical Center Nashville TN USA
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Ferreira SEMM, Soares LM, Lira CR, Yokoyama TS, Engi SA, Cruz FC, Leão RM. Ethanol-induced locomotor sensitization: Neuronal activation in the nucleus accumbens and medial prefrontal cortex. Neurosci Lett 2021; 749:135745. [PMID: 33610663 DOI: 10.1016/j.neulet.2021.135745] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 02/12/2021] [Accepted: 02/15/2021] [Indexed: 12/31/2022]
Abstract
Ethanol consumption may promote neuroplasticity and alterations in synapses, resulting in modifications in neuronal activity. Here, we treated male Swiss mice with ethanol (2.2 g/kg) or saline once per day for 21 consecutive days. Nine days after the last ethanol administration, they received a challenge injection of ethanol or saline, and we assessed locomotor activity. After the behavioral analysis, we evaluated neuronal activation in the medial Prefrontal Cortex (Cingulate, Prelimbic, and Infralimbic) and the Nucleus Accumbens (Shell and Core) using Fos/DAB immunohistochemistry. In another group of animals, we performed the quantitative analysis of the ARC and PSD-95 protein levels by Western blotting in the medial prefrontal cortex and nucleus accumbens brain areas. Repeated ethanol administration produced locomotor sensitization, accompanied by an increase in the nucleus accumbens shell's activation but not core. Furthermore, the ethanol pretreatment reduced ARC expression in the nucleus accumbens and medial prefrontal cortex. Our results suggest the participation of the nucleus accumbens shell in ethanol behavioral sensitization and add new pieces of evidence that neuroplasticity in synapses may contribute to the mechanism underlying this behavior.
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Affiliation(s)
- Sara Emi M M Ferreira
- Department of Bioregulation Sciences, Health Sciences Institute, Federal University of Bahia, UFBA, Brazil; Graduate Program in Pharmacy, Federal University of Bahia, UFBA, Brazil
| | - Leonardo M Soares
- Department of Bioregulation Sciences, Health Sciences Institute, Federal University of Bahia, UFBA, Brazil
| | - Clarice R Lira
- Department of Bioregulation Sciences, Health Sciences Institute, Federal University of Bahia, UFBA, Brazil; Graduate Program in Pharmacy, Federal University of Bahia, UFBA, Brazil
| | - Thais S Yokoyama
- Pharmacology Department, São Paulo Federal University, UNIFESP, Brazil
| | - Sheila A Engi
- Pharmacology Department, São Paulo Federal University, UNIFESP, Brazil
| | - Fábio C Cruz
- Pharmacology Department, São Paulo Federal University, UNIFESP, Brazil
| | - Rodrigo M Leão
- Department of Bioregulation Sciences, Health Sciences Institute, Federal University of Bahia, UFBA, Brazil; Graduate Program in Pharmacy, Federal University of Bahia, UFBA, Brazil; Pharmacology Department, Biomedical Sciences Institute, Federal University of Uberlândia, UFU, Brazil.
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4
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Hauser SR, Waeiss RA, Molosh AI, Deehan GA, Bell RL, McBride WJ, Rodd ZA. Atrial natriuretic peptide (ANP): A novel mechanism for reducing ethanol consumption and seeking behaviors in female alcohol preferring (P) rats. Peptides 2020; 134:170403. [PMID: 32882352 PMCID: PMC7725921 DOI: 10.1016/j.peptides.2020.170403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 08/28/2020] [Accepted: 08/29/2020] [Indexed: 01/04/2023]
Abstract
Atrial Naturietic Peptide (ANP) is a neuropeptide that regulates function of the hypothalamic-pituitary-adrenal (HPA) axis, immune and neuroimmune system, and epigenetic factors. Research has indicated that ANP may mediate alcohol intake, withdrawal, and craving like behaviors. ANP receptors are present in the mesocorticolimbic (MCL) reward pathway of the brain, which includes the nucleus accumbens (Acb) and the ventral tegmental area (VTA). The objectives of the present study were to examine the effects of ANP microinjected into Acb subregions (Shell (Sh), Core (Co), ventral to AcbSh) on operant ethanol (EtOH) self-administration and into posterior VTA (pVTA) on EtOH-seeking behavior of female alcohol-preferring (P) rats. In the first experiment, ANP (0, 10 μg, or 100 μg) was microinjected into subregions of the Acb to determine its effects on EtOH self-administration. In the second experiment, ANP was microinjected into pVTA to determine its effects on Pavlovian Spontaneous Recovery (PSR) of responding, a measure of context-induced EtOH-seeking behavior. Administration of ANP directly into the AcbSh significantly reduced EtOH self-administration compared to vehicle, whereas ANP into the AcbCo or areas directly ventral to the AcbSh did not alter responding for EtOH. Microinjection of ANP into the pVTA significantly reduced responding on the EtOH-associated lever during the PSR test. The data indicate that activation of ANP systems in the (a) AcbSh can inhibit EtOH intake, and (b) in the pVTA can inhibit EtOH-seeking behavior. The results suggest that manipulations of the ANP system could be a potential target for pharmacotherapeutic intervention to treat alcohol use disorder. Supported in part by AA07462, AA07611, AA10717, AA10721, AA013522, AA019366, AA020908, AA022287, and AA024612.
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Affiliation(s)
- Sheketha R Hauser
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - Robert A Waeiss
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Andrei I Molosh
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Gerald A Deehan
- Department of Psychology, East Tennessee State University, Johnson City, TN, USA
| | - Richard L Bell
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - William J McBride
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Zachary A Rodd
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, USA; Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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5
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Strong CE, Hagarty DP, Brea Guerrero A, Schoepfer KJ, Cajuste SM, Kabbaj M. Chemogenetic selective manipulation of nucleus accumbens medium spiny neurons bidirectionally controls alcohol intake in male and female rats. Sci Rep 2020; 10:19178. [PMID: 33154463 PMCID: PMC7644642 DOI: 10.1038/s41598-020-76183-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 10/20/2020] [Indexed: 12/11/2022] Open
Abstract
The nucleus accumbens (NAc), considered the hub of reward circuitry, is comprised of two medium spiny neuron (MSN) subtypes that are classified by their enrichment of dopamine 1 (D1) or 2 (D2) receptors. While reports indicate that alcohol increases excitatory neurotransmission exclusively on NAc D1-MSNs in male rats, it remains unknown how NAc MSNs control alcohol intake in either sex. Therefore, this study investigated how NAc MSNs mediate alcohol intake by using Drd1a-iCre and Drd2-iCre transgenic rats of both sexes. Intra-NAc infusions of Cre-inducible viral vectors containing stimulatory (hM3Dq) or inhibitory (hM4Di) designer receptors exclusively activated by designer drugs (DREADDs) were delivered after 4-weeks of alcohol intake, and clozapine-N-oxide (CNO) was administered to selectively manipulate NAc MSNs. Our results show that activation of NAc D1-MSNs increased alcohol intake 1-, 4-, and 24-h after the start of drinking while inhibition decreased it 1-h after the start of drinking, with no sex differences observed at any time point. Activation of NAc D2-MSNs had no impact on alcohol intake while inhibition increased alcohol intake in Drd2-iCre rats for 1-h in males and 4-h in females. These findings suggest opposing roles for how NAc D1- and D2-MSNs modulate alcohol intake in rats of both sexes.
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Affiliation(s)
- C E Strong
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA
| | - D P Hagarty
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA
| | - A Brea Guerrero
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA
| | - K J Schoepfer
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA
| | - S M Cajuste
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA
| | - M Kabbaj
- Program in Neuroscience, Department of Biomedical Sciences, Florida State University, Medical Science Research, Room 3300-H, 1115 W. Call St., Tallahassee, FL, 32306, USA.
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6
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Hauser SR, Knight CP, Truitt WA, Waeiss RA, Holt IS, Carvajal GB, Bell RL, Rodd ZA. Adolescent Intermittent Ethanol Increases the Sensitivity to the Reinforcing Properties of Ethanol and the Expression of Select Cholinergic and Dopaminergic Genes within the Posterior Ventral Tegmental Area. Alcohol Clin Exp Res 2019; 43:1937-1948. [DOI: 10.1111/acer.14150] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 07/10/2019] [Indexed: 01/12/2023]
Affiliation(s)
- Sheketha R. Hauser
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
| | | | - William A. Truitt
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
| | - Robert Aaron Waeiss
- Program in Medical Neuroscience Paul and Carole Stark Neurosciences Research Institute Indiana University School of Medicine Indianapolis Indiana
| | - Ian S. Holt
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
| | - Gustavo B. Carvajal
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
| | - Richard L. Bell
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
| | - Zachary A. Rodd
- Department of Psychiatry Indiana University School of Medicine Indianapolis Indiana
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7
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Neuro-hormonal mechanisms underlying changes in reward related behaviors following weight loss surgery: Potential pharmacological targets. Biochem Pharmacol 2019; 164:106-114. [DOI: 10.1016/j.bcp.2019.04.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/03/2019] [Indexed: 12/11/2022]
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Lei K, Kwok C, Darevsky D, Wegner SA, Yu J, Nakayama L, Pedrozo V, Anderson L, Ghotra S, Fouad M, Hopf FW. Nucleus Accumbens Shell Orexin-1 Receptors Are Critical Mediators of Binge Intake in Excessive-Drinking Individuals. Front Neurosci 2019; 13:88. [PMID: 30814925 PMCID: PMC6381036 DOI: 10.3389/fnins.2019.00088] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 01/25/2019] [Indexed: 12/29/2022] Open
Abstract
Excessive, binge alcohol drinking is a potent and pernicious obstacle to treating alcohol use disorder (AUD), and heavy-drinking humans are responsible for much of the substantial costs and harms of AUD. Thus, identifying key mechanisms that drive intake in higher-drinking individuals may provide important, translationally useful therapeutic interventions. Orexin-1-receptors (Ox1Rs) promote states of high motivation, and studies with systemic Ox1R inhibition suggest a particular role in individuals with higher intake levels. However, little has been known about circuits where Ox1Rs promote pathological intake, especially excessive alcohol consumption. We previously discovered that binge alcohol drinking requires Ox1Rs in medial nucleus accumbens shell (Shell), using two-bottle-choice Drinking-in-the-Dark (2bc-DID) in adult, male C57BL/6 mice. Here, we show that Shell Ox1Rs promoted intake during intermittent-access alcohol drinking as well as 2bc-DID, and that Shell inhibition with muscimol/baclofen also suppressed 2bc-DID intake. Importantly, with this large data set, we were able to demonstrate that Shell Ox1Rs and overall activity were particularly important for driving alcohol consumption in higher-drinking individuals, with little overall impact in moderate drinkers. Shell inhibition results were compared with control data combined from drug treatments that did not reduce intake, including NMDAR or PKC inhibition in Shell, Ox1R inhibition in accumbens core, and systemic inhibition of dopamine-1 receptors; these were used to understand whether more specific Shell Ox1R contributions in higher drinkers might simply result from intrinsic variability in mouse drinking. Ineffectiveness of Shell inhibition in moderate-drinkers was not due to a floor effect, since systemic baclofen reduced alcohol drinking regardless of basal intake levels, without altering concurrent water intake or saccharin consumption. Finally, alcohol intake in the first exposure predicted consumption levels weeks later, suggesting that intake level may be a stable trait in each individual. Together, our studies indicate that Shell Ox1Rs are critical mediators of binge alcohol intake in higher-drinking individuals, with little net contribution to alcohol drinking in more moderate bingers, and that targeting Ox1Rs may substantially reduce AUD-related harms.
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Affiliation(s)
- Kelly Lei
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Claudina Kwok
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - David Darevsky
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Scott A Wegner
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - JiHwan Yu
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Lisa Nakayama
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Vincent Pedrozo
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Lexy Anderson
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Shahbaj Ghotra
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Mary Fouad
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Frederic W Hopf
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
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9
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Burns JA, Kroll DS, Feldman DE, Kure Liu C, Manza P, Wiers CE, Volkow ND, Wang GJ. Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders. Front Psychiatry 2019; 10:626. [PMID: 31620026 PMCID: PMC6759955 DOI: 10.3389/fpsyt.2019.00626] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 08/05/2019] [Indexed: 12/21/2022] Open
Abstract
Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.
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Affiliation(s)
- Jamie A Burns
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
| | - Danielle S Kroll
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
| | - Dana E Feldman
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
| | | | - Peter Manza
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
| | - Corinde E Wiers
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
| | - Nora D Volkow
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States.,National Institute on Drug Abuse, Bethesda, MD, United States
| | - Gene-Jack Wang
- National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, United States
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Althobaiti YS, Alshehri FS, Hakami AY, Hammad AM, Sari Y. Effects of Clavulanic Acid Treatment on Reinstatement to Methamphetamine, Glial Glutamate Transporters, and mGluR 2/3 Expression in P Rats Exposed to Ethanol. J Mol Neurosci 2018; 67:1-15. [PMID: 30471010 DOI: 10.1007/s12031-018-1194-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 10/01/2018] [Indexed: 11/24/2022]
Abstract
Evidence demonstrated that the glutamatergic system is implicated in mediating relapse to several drugs of abuse, including methamphetamine (METH). Glutamate homeostasis is maintained by a number of glutamate transporters, such as glutamate transporter type 1 (GLT-1), cystine/glutamate transporter (xCT), and glutamate aspartate transporter (GLAST). In addition, group II metabotropic glutamate receptors (mGluR2/3) were found to be implicated in relapse-seeking behavior. Ample evidence showed that β-lactam antibiotics are effective in upregulating GLT-1 and xCT expression, thus improving glutamate homeostasis and attenuating relapse to drugs of abuse. In this study, we investigated the reinstatement of METH using conditioned place preference (CPP) in male alcohol-preferring (P) rats exposed to home-cage free choice ethanol drinking. Here, we tested the effect of clavulanic acid (CA), a β-lactam, on the reinstatement of METH-seeking and ethanol drinking. In addition, we examined the expression of GLT-1, xCT, and GLAST as well as metabotropic glutamate receptor (mGluR2/3) in the nucleus accumbens (NAc) shell, NAc core, and dorsomedial prefrontal cortex (dmPFC). A priming i.p. injection of METH reinstated preference in METH-paired chamber following extinction. Chronic exposure to ethanol decreased the expression of GLT-1 and xCT in the NAc shell, but not in the NAc core or dmPFC. CA treatment blocked the reinstatement of METH-seeking, decreased ethanol intake, and restored the expression of GLT-1 and xCT in the NAc shell. In addition, the expression of mGluR2/3 was increased by CA treatment in the NAc shell and dmPFC. These findings suggest that these glutamate transporters and mGluR2/3 might be potential therapeutic targets for the attenuation of reinstatement to METH-seeking.
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Affiliation(s)
- Yusuf S Althobaiti
- College of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology and Experimental Therapeutics, University of Toledo, Health Science Campus, 3000 Arlington Avenue, HEB 282G, Toledo, OH, 43614, USA.,College of Pharmacy, Department of Pharmacology and Toxicology, Taif University, Taif, Saudi Arabia
| | - Fahad S Alshehri
- College of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology and Experimental Therapeutics, University of Toledo, Health Science Campus, 3000 Arlington Avenue, HEB 282G, Toledo, OH, 43614, USA
| | - Alqassem Y Hakami
- College of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology and Experimental Therapeutics, University of Toledo, Health Science Campus, 3000 Arlington Avenue, HEB 282G, Toledo, OH, 43614, USA
| | - Alaa M Hammad
- College of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology and Experimental Therapeutics, University of Toledo, Health Science Campus, 3000 Arlington Avenue, HEB 282G, Toledo, OH, 43614, USA
| | - Youssef Sari
- College of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology and Experimental Therapeutics, University of Toledo, Health Science Campus, 3000 Arlington Avenue, HEB 282G, Toledo, OH, 43614, USA.
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11
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Bell RL, Hauser SR, Liang T, Sari Y, Maldonado-Devincci A, Rodd ZA. Rat animal models for screening medications to treat alcohol use disorders. Neuropharmacology 2017; 122:201-243. [PMID: 28215999 PMCID: PMC5659204 DOI: 10.1016/j.neuropharm.2017.02.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Revised: 02/02/2017] [Accepted: 02/05/2017] [Indexed: 01/21/2023]
Abstract
The purpose of this review is to present animal research models that can be used to screen and/or repurpose medications for the treatment of alcohol abuse and dependence. The focus will be on rats and in particular selectively bred rats. Brief introductions discuss various aspects of the clinical picture, which provide characteristics of individuals with alcohol use disorders (AUDs) to model in animals. Following this, multiple selectively bred rat lines will be described and evaluated in the context of animal models used to screen medications to treat AUDs. Next, common behavioral tests for drug efficacy will be discussed particularly as they relate to stages in the addiction cycle. Tables highlighting studies that have tested the effects of compounds using the respective techniques are included. Wherever possible the Tables are organized chronologically in ascending order to describe changes in the focus of research on AUDs over time. In general, high ethanol-consuming selectively bred rats have been used to test a wide range of compounds. Older studies usually followed neurobiological findings in the selected lines that supported an association with a propensity for high ethanol intake. Most of these tests evaluated the compound's effects on the maintenance of ethanol drinking. Very few compounds have been tested during ethanol-seeking and/or relapse and fewer still have assessed their effects during the acquisition of AUDs. Overall, while a substantial number of neurotransmitter and neuromodulatory system targets have been assessed; the roles of sex- and age-of-animal, as well as the acquisition of AUDs, ethanol-seeking and relapse continue to be factors and behaviors needing further study. This article is part of the Special Issue entitled "Alcoholism".
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Affiliation(s)
- Richard L Bell
- Indiana University School of Medicine, Department of Psychiatry, Indianapolis, IN 46202, USA.
| | - Sheketha R Hauser
- Indiana University School of Medicine, Department of Psychiatry, Indianapolis, IN 46202, USA
| | - Tiebing Liang
- Indiana University School of Medicine, Department of Gastroenterology, Indianapolis, IN 46202, USA
| | - Youssef Sari
- University of Toledo, Department of Pharmacology, Toledo, OH 43614, USA
| | | | - Zachary A Rodd
- Indiana University School of Medicine, Department of Psychiatry, Indianapolis, IN 46202, USA
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Cannady R, McGonigal JT, Newsom RJ, Woodward JJ, Mulholland PJ, Gass JT. Prefrontal Cortex K Ca2 Channels Regulate mGlu 5-Dependent Plasticity and Extinction of Alcohol-Seeking Behavior. J Neurosci 2017; 37:4359-4369. [PMID: 28320841 PMCID: PMC5413180 DOI: 10.1523/jneurosci.2873-16.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 03/10/2017] [Accepted: 03/15/2017] [Indexed: 12/17/2022] Open
Abstract
Identifying novel treatments that facilitate extinction learning could enhance cue-exposure therapy and reduce high relapse rates in alcoholics. Activation of mGlu5 receptors in the infralimbic prefrontal cortex (IL-PFC) facilitates learning during extinction of cue-conditioned alcohol-seeking behavior. Small-conductance calcium-activated potassium (KCa2) channels have also been implicated in extinction learning of fear memories, and mGlu5 receptor activation can reduce KCa2 channel function. Using a combination of electrophysiological, pharmacological, and behavioral approaches, this study examined KCa2 channels as a novel target to facilitate extinction of alcohol-seeking behavior in rats. This study also explored related neuronal and synaptic mechanisms within the IL-PFC that underlie mGlu5-dependent enhancement of extinction learning. Using whole-cell patch-clamp electrophysiology, activation of mGlu5 in ex vivo slices significantly reduced KCa2 channel currents in layer V IL-PFC pyramidal neurons, confirming functional downregulation of KCa2 channel activity by mGlu5 receptors. Additionally, positive modulation of KCa2 channels prevented mGlu5 receptor-dependent facilitation of long-term potentiation in the IL-PFC. Systemic and intra-IL-PFC treatment with apamin (KCa2 channel allosteric inhibitor) significantly enhanced extinction of alcohol-seeking behavior across multiple extinction sessions, an effect that persisted for 3 weeks, but was not observed after apamin microinfusions into the prelimbic PFC. Positive modulation of IL-PFC KCa2 channels significantly attenuated mGlu5-dependent facilitation of alcohol cue-conditioned extinction learning. These data suggest that mGlu5-dependent facilitation of extinction learning and synaptic plasticity in the IL-PFC involves functional inhibition of KCa2 channels. Moreover, these findings demonstrate that KCa2 channels are a novel target to facilitate long-lasting extinction of alcohol-seeking behavior.SIGNIFICANCE STATEMENT Alcohol use disorder is a chronic relapsing disorder that is associated with compulsive alcohol-seeking behavior. One of the main causes of alcohol relapse is the craving caused by environmental cues that are associated with alcohol. These cues are formed by normal learning and memory principles, and the understanding of the brain mechanisms that help form these associations can lead to the development of drugs and/or behavior therapies that reduce the impact that these cues have on relapse in alcoholics.
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Affiliation(s)
- Reginald Cannady
- Department of Neuroscience
- Department of Psychiatry & Behavioral Sciences, and
| | | | | | - John J Woodward
- Department of Neuroscience
- Department of Psychiatry & Behavioral Sciences, and
| | | | - Justin T Gass
- Department of Neuroscience,
- Department of Psychiatry & Behavioral Sciences, and
- Charleston Alcohol Research Center, Addiction Sciences Division, College of Health Professions, Medical University of South Carolina, Charleston, South Carolina 29425
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13
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Contrasting effects of 5-HT 3 receptor stimulation of the nucleus accumbens or ventral tegmentum on food intake in the rat. Behav Brain Res 2017; 323:15-23. [PMID: 28115218 DOI: 10.1016/j.bbr.2017.01.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 01/17/2017] [Accepted: 01/18/2017] [Indexed: 11/22/2022]
Abstract
Although serotonin (5-HT) signaling is known to regulate food intake and energy homeostasis, the roles of the 5-HT3 receptor in feeding processes have been elusive. 5-HT3 receptors are found throughout mesolimbic circuitry that promote feeding not only in response to hunger, but also to the palatable and rewarding properties of food. These experiments examined if stimulation or blockade of the 5-HT3 receptor of the nucleus accumbens (NAcc) or ventral tegmentum affected food intake in the rat in response to hunger or the presence of a palatable diet. Rats (N=6-9/group) received bilateral injections of the 5-HT3 agonist m-chlorophenylbiguanide hydrochloride (mCPBG; at 0.0, 10.0, or 20.0μg/0.5μl/side) or the 5-HT3 antagonist ondansetron hydrochloride (at 0.0, 1.0, 2.0, or 5.0μg/0.5μl/side) into either the NAcc or the ventral tegmentum. NAcc 5-HT3 receptor stimulation significantly increased 2-h food intake in food-deprived animals offered rat chow and in a separate group of unrestricted rats offered a sweetened fat diet. In contrast to the feeding increase seen with NAcc treatments, stimulation of 5-HT3 receptors of the ventral tegmentum significantly reduced food and water intake in food-restricted animals; reductions of intake in non-restricted rats offered the palatable diet did not approach significance. Blockade of the 5-HT3 receptor had no effect on feeding in either brain region. These data support a functional role for serotonergic signaling in the mesolimbic pathway on motivated behavior, and demonstrate that 5-HT3 receptors differentially modulate food consumption in a region-dependent manner.
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Spoelder M, Hesseling P, Styles M, Baars AM, Lozeman-van 't Klooster JG, Lesscher HMB, Vanderschuren LJMJ. Dopaminergic neurotransmission in ventral and dorsal striatum differentially modulates alcohol reinforcement. Eur J Neurosci 2016; 45:147-158. [PMID: 27521051 DOI: 10.1111/ejn.13358] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 07/14/2016] [Accepted: 08/02/2016] [Indexed: 01/18/2023]
Abstract
Dopaminergic neurotransmission in the striatum has been widely implicated in the reinforcing properties of substances of abuse. However, the striatum is functionally heterogeneous, and previous work has mostly focused on psychostimulant drugs. Therefore, we investigated how dopamine within striatal subregions modulates alcohol-directed behaviour in rats. We assessed the effects of infusion of the dopamine receptor antagonist alpha-flupenthixol into the shell and core of the nucleus accumbens (NAcc) and the dorsolateral striatum (DLS) on responding for alcohol under fixed ratio 1 (FR1) and progressive ratio (PR) schedules of reinforcement. Bilateral infusion of alpha-flupenthixol into the NAcc shell reduced responding for alcohol under both the FR1 (15 μg/side) and the PR schedule (3.75-15 μg/side) of reinforcement. Infusion of alpha-flupenthixol into the NAcc core (7.5-15 μg/side) also decreased responding for alcohol under both schedules. By contrast, alpha-flupenthixol infusion into the DLS did not affect FR1 responding, but reduced responding under the PR schedule (15 μg/side). The decreases in responding were related to earlier termination of responding during the session, whereas the onset and rate of responding remained largely unaffected. Together, these data suggest that dopamine in the NAcc shell is involved in the incentive motivation for alcohol, whereas DLS dopamine comes into play when obtaining alcohol requires high levels of effort. In contrast, NAcc core dopamine appears to play a more general role in alcohol reinforcement. In conclusion, dopaminergic neurotransmission acts in concert in subregions of the striatum to modulate different aspects of alcohol-directed behaviour.
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Affiliation(s)
- Marcia Spoelder
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - Peter Hesseling
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - Matthew Styles
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - Annemarie M Baars
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - José G Lozeman-van 't Klooster
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - Heidi M B Lesscher
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
| | - Louk J M J Vanderschuren
- Department of Animals in Science and Society, Division of Behavioural Neuroscience, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
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Effects of DA-Phen, a dopamine-aminoacidic conjugate, on alcohol intake and forced abstinence. Behav Brain Res 2016; 310:109-18. [DOI: 10.1016/j.bbr.2016.05.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 12/27/2022]
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16
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Lei K, Wegner SA, Yu JH, Mototake A, Hu B, Hopf FW. Nucleus Accumbens Shell and mPFC but Not Insula Orexin-1 Receptors Promote Excessive Alcohol Drinking. Front Neurosci 2016; 10:400. [PMID: 27625592 PMCID: PMC5004043 DOI: 10.3389/fnins.2016.00400] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/15/2016] [Indexed: 12/22/2022] Open
Abstract
Addiction to alcohol remains a major social and economic problem, in part because of the high motivation for alcohol that humans exhibit and the hazardous binge intake this promotes. Orexin-1-type receptors (OX1Rs) promote reward intake under conditions of strong drives for reward, including excessive alcohol intake. While systemic modulation of OX1Rs can alter alcohol drinking, the brain regions that mediate this OX1R enhancement of excessive drinking remain unknown. Given the importance of the nucleus accumbens (NAc) and anterior insular cortex (aINS) in driving many addictive behaviors, including OX1Rs within these regions, we examined the importance of OX1Rs in these regions on excessive alcohol drinking in C57BL/6 mice during limited-access alcohol drinking in the dark cycle. Inhibition of OX1Rs with the widely used SB-334867 within the medial NAc Shell (mNAsh) significantly reduced drinking of alcohol, with no effect on saccharin intake, and no effect on alcohol consumption when infused above the mNAsh. In contrast, intra-mNAsh infusion of the orexin-2 receptor TCS-OX2-29 had no impact on alcohol drinking. In addition, OX1R inhibition within the aINS had no effect on excessive drinking, which was surprising given the importance of aINS-NAc circuits in promoting alcohol consumption and the role for aINS OX1Rs in driving nicotine intake. However, OX1R inhibition within the mPFC did reduce alcohol drinking, indicating cortical OXR involvement in promoting intake. Also, in support of the critical role for mNAsh OX1Rs, SB within the mNAsh also significantly reduced operant alcohol self-administration in rats. Finally, orexin ex vivo enhanced firing in mNAsh neurons from alcohol-drinking mice, with no effect on evoked EPSCs or input resistance; a similar orexin increase in firing without a change in input resistance was observed in alcohol-naïve mice. Taken together, our results suggest that OX1Rs within the mNAsh and mPFC, but not the aINS, play a central role in driving excessive alcohol drinking.
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Affiliation(s)
- Kelly Lei
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
| | - Scott A Wegner
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
| | - Ji Hwan Yu
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
| | - Arisa Mototake
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
| | - Bing Hu
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
| | - Frederic W Hopf
- Alcohol and Addiction Research Group, Department of Neurology, University of California, San Francisco San Francisco, CA, USA
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Modulation of nucleus accumbens connectivity by alcohol drinking and naltrexone in alcohol-preferring rats: A manganese-enhanced magnetic resonance imaging study. Eur Neuropsychopharmacol 2016; 26:445-55. [PMID: 26851200 DOI: 10.1016/j.euroneuro.2016.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 12/31/2015] [Accepted: 01/15/2016] [Indexed: 11/23/2022]
Abstract
The nonselective opioid receptor antagonist naltrexone is now used for the treatment of alcoholism, yet naltrexone's central mechanism of action remains poorly understood. One line of evidence suggests that opioid antagonists regulate alcohol drinking through interaction with the mesolimbic dopamine system. Hence, our goal here was to examine the role of the nucleus accumbens connectivity in alcohol reinforcement and naltrexone's actions using manganese-enhanced magnetic resonance imaging (MEMRI). Following long-term free-choice drinking of alcohol and water, AA (Alko Alcohol) rats received injections of MnCl2 into the nucleus accumbens for activity-dependent tracing of accumbal connections. Immediately after the accumbal injections, rats were imaged using MEMRI, and then allowed to drink either alcohol or water for the next 24h. Naltrexone was administered prior to the active dark period, and the second MEMRI was performed 24h after the first scan. Comparison of signal intensity at 1 and 24h after accumbal MnCl2 injections revealed an ipsilateral continuum through the ventral pallidum, bed nucleus of the stria terminalis, globus pallidus, and lateral hypothalamus to the substantia nigra and ventral tegmental area. Activation was also seen in the rostral part of the insular cortex and regions of the prefrontal cortex. Alcohol drinking resulted in enhanced activation of these connections, whereas naltrexone suppressed alcohol-induced activity. These data support the involvement of the accumbal connections in alcohol reinforcement and mediation of naltrexone's suppressive effects on alcohol drinking through their deactivation.
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