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Mason B, Calhoun C, Woytowicz V, Pina L, Kanda R, Dunn C, Alves A, Donaldson ST. CXCR4 inhibition with AMD3100 attenuates amphetamine induced locomotor activity in adolescent Long Evans male rats. PLoS One 2021; 16:e0247707. [PMID: 33647040 PMCID: PMC7920371 DOI: 10.1371/journal.pone.0247707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 02/11/2021] [Indexed: 02/02/2023] Open
Abstract
Adolescent psychostimulant abuse has been on the rise over the past decade. This trend has demonstrable ramifications on adolescent behavior and brain morphology, increasing risk for development of addiction during adolescence and in later adulthood. Neuroimmune substrates are implicated in the etiology of substance use disorders. To add to this body of work, the current study was developed to explore the role of a chemokine receptor, CXC Chemokine Receptor 4 (CXCR4), in the development of amphetamine (AMPH) sensitization. We targeted CXCR4 as it is implicated in developmental processes, dopaminergic transmission, neuroimmune responses, and the potentiation of psychostimulant abuse pathology. To evaluate the role of CXCR4 activity on the development of AMPH sensitization, a CXCR4 antagonist (Plerixafor; AMD3100) was administered to rats as a pretreatment variable. Specifically, adolescent Long Evans male rats (N = 37) were divided into four groups: (1) AMD3100 (IP, 4.0 mg/kg) + AMPH (IP, 4.0 mg/kg), (2) saline (SAL; 0.9% NaCl) + AMPH, (3) AMD3100 + SAL, and (4) SAL + SAL. Animals were first habituated to locomotor activity (LMA) chambers, then injected with a pretreatment drug (AMD3100 or SAL) followed by AMPH or SAL every other for four days. After a one-week withdrawal period, all animals were administered a low challenge dose of AMPH (IP, 1.0 mg/kg). AMPH-injected rats displayed significantly more locomotor activity compared to controls across all testing days. CXCR4 antagonism significantly attenuated AMPH-induced locomotor activity. On challenge day, AMD3100 pre-treated animals exhibited diminutive AMPH-induced locomotor activity compared to SAL pre-treated animals. Postmortem analyses of brain tissue revealed elevated CXCR4 protein levels in the striatum of all experimental groups. Our results implicate CXCR4 signaling in the development of AMPH sensitization and may represent an important therapeutic target for future research in psychostimulant abuse.
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Affiliation(s)
- Briana Mason
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
- * E-mail:
| | - Corey Calhoun
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Victoria Woytowicz
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Latifa Pina
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Roshninder Kanda
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Curtis Dunn
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Antonio Alves
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - S. Tiffany Donaldson
- Department of Psychology, University of Massachusetts Boston, Boston, Massachusetts, United States of America
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GABAergic mRNA expression is differentially expressed across the prelimbic and orbitofrontal cortices of rats sensitized to methamphetamine: Relevance to psychosis. Neuropharmacology 2016; 111:107-118. [PMID: 27580848 DOI: 10.1016/j.neuropharm.2016.08.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 08/25/2016] [Accepted: 08/27/2016] [Indexed: 12/30/2022]
Abstract
Psychotic disorders, such as schizophrenia, are characterized by prevalent and persistent executive deficits that are believed to be the result of dysfunctional inhibitory gamma-aminobutyric acid (GABA) processing of the prefrontal cortex (PFC). Methamphetamine (METH) is a commonly used psychostimulant that can induce psychotic and cognitive symptoms that are indistinguishable to schizophrenia, suggesting that METH-induced psychosis may have a similar GABAergic profile of the PFC. As the PFC consists of multiple subregions, the aim of the current study was to investigate changes to GABAergic mRNA expression in the prelimbic (PRL) and orbitofrontal (OFC) cortices of the PFC in rats sensitized to repeated METH administration. Male Sprague Dawley rats underwent daily METH or saline injections for 7 days. Following 14 days of withdrawal, rats were challenged with acute METH administration, RNA was isolated from the PRL and OFC and quantitative PCR was used to compare the relative expression of GABA enzymes, transporters, metabolites and receptor subunits. GAD67, GAD65, GAT1, GAT3, VGAT and GABAT mRNA expression were upregulated in the PRL. Ionotropic GABAA receptor subunits α1, α3, α5 and β2 were specifically upregulated in the OFC. These findings suggest that alterations to GABAergic mRNA expression following sensitization to METH are biologically dissociated between the OFC and PRL, suggesting that GABAergic gene expression is significantly altered following chronic METH exposure in a brain-region and GABA-specific manner. These changes may lead to profound consequences on central inhibitory mechanisms of localized regions of the PFC and may underpin common behavioral phenotypes seen across psychotic disorders.
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Aguilar-Rivera M, Casanova J, Gatica R, Quirk G, Fuentealba J. Amphetamine sensitization is accompanied by an increase in prelimbic cortex activity. Neuroscience 2015; 288:1-9. [DOI: 10.1016/j.neuroscience.2014.12.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 11/30/2014] [Accepted: 12/17/2014] [Indexed: 10/24/2022]
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Buchta WC, Riegel AC. Chronic cocaine disrupts mesocortical learning mechanisms. Brain Res 2015; 1628:88-103. [PMID: 25704202 DOI: 10.1016/j.brainres.2015.02.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/28/2015] [Accepted: 02/01/2015] [Indexed: 01/06/2023]
Abstract
The addictive power of drugs of abuse such as cocaine comes from their ability to hijack natural reward and plasticity mechanisms mediated by dopamine signaling in the brain. Reward learning involves burst firing of midbrain dopamine neurons in response to rewards and cues predictive of reward. The resulting release of dopamine in terminal regions is thought to act as a teaching signaling to areas such as the prefrontal cortex and striatum. In this review, we posit that a pool of extrasynaptic dopaminergic D1-like receptors activated in response to dopamine neuron burst firing serve to enable synaptic plasticity in the prefrontal cortex in response to rewards and their cues. We propose that disruptions in these mechanisms following chronic cocaine use contribute to addiction pathology, in part due to the unique architecture of the mesocortical pathway. By blocking dopamine reuptake in the cortex, cocaine elevates dopamine signaling at these extrasynaptic receptors, prolonging D1-receptor activation and the subsequent activation of intracellular signaling cascades, and thus inducing long-lasting maladaptive plasticity. These cellular adaptations may account for many of the changes in cortical function observed in drug addicts, including an enduring vulnerability to relapse. Therefore, understanding and targeting these neuroadaptations may provide cognitive benefits and help prevent relapse in human drug addicts.
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Affiliation(s)
- William C Buchta
- Neurobiology of Addiction Research Center (NARC), Medical University of South Carolina, Charleston, SC 29425, USA
| | - Arthur C Riegel
- Neurobiology of Addiction Research Center (NARC), Medical University of South Carolina, Charleston, SC 29425, USA.
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Crocker CE, Bernier DC, Hanstock CC, Lakusta B, Purdon SE, Seres P, Tibbo PG. Prefrontal glutamate levels differentiate early phase schizophrenia and methamphetamine addiction: a (1)H MRS study at 3Tesla. Schizophr Res 2014; 157:231-7. [PMID: 24906219 DOI: 10.1016/j.schres.2014.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 05/05/2014] [Accepted: 05/09/2014] [Indexed: 01/22/2023]
Abstract
Acute symptoms of methamphetamine-induced psychosis are similar to those of primary schizophrenia. Understanding similarities or differences in the biological substrate of these psychoses could lead to early differentiation of these two clinical conditions resulting in more efficient treatment strategies. Proton magnetic resonance spectroscopy was acquired from the medial prefrontal cortex in 29 unmedicated patients with first episode of psychosis (FEP), 29 abstinent methamphetamine-addicted people (METH) and 45 healthy controls (HCs) (age range 17.3 to 29.9years old). The METH group displayed robust reductions in concentration levels of glutamate (Glu) relative to FEP (Cohen's d=1.20) and HC (d=0.87). The METH group also displayed reduced levels of N-acetylaspartate (NAA) relative to FEP (d=0.53) and HC (d=0.76). The HC group displayed a positive association between levels of Glu and NAA, r(45)=0.52, p<0.001, while the two clinical groups failed to show this normal association. This suggests that the cellular metabolism is altered in both conditions. These data support the assumption that cellular abnormalities differ between primary schizophrenia and methamphetamine addiction despite the overlap in clinical presentation.
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Affiliation(s)
- Candice E Crocker
- Department of Psychiatry, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Denise C Bernier
- Department of Psychiatry, Dalhousie University, Halifax, Nova Scotia, Canada
| | | | - Bonnie Lakusta
- Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Scot E Purdon
- Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter Seres
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Philip G Tibbo
- Department of Psychiatry, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada.
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The influence of ionotropic and metabotropic glutamate receptor ligands on anxiety-like effect of amphetamine withdrawal in rats. Prog Neuropsychopharmacol Biol Psychiatry 2013; 45:242-9. [PMID: 23623810 DOI: 10.1016/j.pnpbp.2013.04.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 04/17/2013] [Accepted: 04/19/2013] [Indexed: 01/22/2023]
Abstract
Chronic amphetamine use results in anxiety-like states after drug cessation. The aim of the study was to determine a role of ionotropic and metabotropic glutamate receptor ligands in amphetamine-evoked withdrawal anxiety in the elevated plus-maze test in rats. In our study memantine (8 and 12 mg/kg), a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist did not reduce amphetamine withdrawal anxiety. Acamprosate (NMDA and metabotropic glutamate 5 receptor (mGluR5) antagonist) at the dose 200 and 400mg/kg showed anxiolytic-like effect, thus increasing the percent of time spent in open arms and a number of open arm entries. mGluR5 selective antagonist, MTEP (3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine hydrochloride) and mGluR2/3 agonist, LY354740 (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid), caused effects similar to acamprosate at doses 1.25-5mg/kg and 2.5-5mg/kg, respectively. None of the glutamate ligands influenced locomotor activity of rats when given to the saline-treated group. Taking into account the positive correlation between amphetamine withdrawal-induced anxiety and relapse to amphetamine taking, our results suggest that modulation of mGluRs may prevent relapse to amphetamine and might pose a new direction in amphetamine abuse therapy.
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Sherrill LK, Stanis JJ, Gulley JM. Age-dependent effects of repeated amphetamine exposure on working memory in rats. Behav Brain Res 2013; 242:84-94. [PMID: 23291159 DOI: 10.1016/j.bbr.2012.12.044] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/20/2012] [Accepted: 12/24/2012] [Indexed: 11/27/2022]
Abstract
Cognitive dysfunction is a hallmark of chronic psychostimulant misuse. Adolescents may have heightened risk of developing drug-induced deficits because their brains are already undergoing widespread changes in anatomy and function as a normal part of development. To address this hypothesis, we performed two sets of experiments where adolescent and young adult rats were pre-exposed to saline or amphetamine (1 or 3mg/kg) and subsequently tested in a prefrontal cortex (PFC)-sensitive working memory task. A total of ten injections of AMPH or saline (in control rats) were given every other day over the course of 19 days. After rats reached adulthood (>90 days old), cognitive performance was assessed using operant-based delayed matching-to-position (DMTP) and delayed nonmatching-to-position (DNMTP) tasks. DNMTP was also assessed following challenges with amphetamine (0.3-1.25mg/kg), and ketamine (5.0-10mg/kg). In experiment one, we also measured the locomotor response following the first and tenth pre-exposure to amphetamine and after an amphetamine challenge given at the conclusion of operant testing. Compared to adult-exposed groups, adolescents were less sensitive to the psychomotor effects of amphetamine. However, they were more vulnerable to exposure-induced cognitive impairments. For example, adolescent-exposed rats displayed delay-dependent deficits in accuracy, increased sensitivity to proactive interference, and required more training to reach criterion. Drug challenges produced deficits in DNMTP performance, but these were not dependent on pre-exposure group. These studies demonstrate age of exposure-dependent effects of amphetamine on cognition in a PFC-sensitive task, suggesting a heightened sensitivity of adolescents to amphetamine-induced neuroplasticity.
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Affiliation(s)
- Luke K Sherrill
- Department of Psychology, University of Illinois, Urbana-Champaign, USA
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Casanova JP, Velis GP, Fuentealba JA. Amphetamine locomotor sensitization is accompanied with an enhanced high K⁺-stimulated Dopamine release in the rat medial prefrontal cortex. Behav Brain Res 2012; 237:313-7. [PMID: 23047059 DOI: 10.1016/j.bbr.2012.09.052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 09/26/2012] [Accepted: 09/30/2012] [Indexed: 11/16/2022]
Abstract
In the present work, we assessed dopamine extracellular levels in the medial Prefrontal Cortex of rats repeatedly treated with amphetamine during early abstinence. Rats were injected once daily with amphetamine for five consecutive days. A sensitized locomotor response was observed in 55% of animals treated. After two days of abstinence, an amphetamine challenge dose was given to all rats and locomotor activity was measured to assess expression of sensitization. A persistence of heightened locomotor response to amphetamine was observed in rats that developed sensitization. Twenty four hours after amphetamine challenge, microdialysis experiments were carried out to evaluate basal and stimulated dopamine extracellular levels in the medial Prefrontal Cortex. Rats that developed and expressed amphetamine locomotor sensitization showed a significantly greater high potassium-stimulated dopamine release compared to Non-sensitized and Saline rats. These results show that the increased dopamine releasability in the medial Prefrontal Cortex occurs soon after development of amphetamine locomotor sensitization, and might be underlying the early expression of sensitization.
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Affiliation(s)
- José Patricio Casanova
- Millenium Science Nucleus in Stress and Addiction, Pontificia Universidad Católica de Chile, Santiago, Chile
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Repeated amphetamine exposure disrupts dopaminergic modulation of amygdala-prefrontal circuitry and cognitive/emotional functioning. J Neurosci 2011; 31:11282-94. [PMID: 21813688 DOI: 10.1523/jneurosci.1810-11.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Repeated exposure to psychostimulants such as amphetamine (AMPH) disrupts cognitive and behavioral processes mediated by the medial prefrontal cortical (mPFC) and basolateral amygdala (BLA). The present study investigated the effects of repeated AMPH exposure on the neuromodulatory actions of dopamine (DA) on BLA-mPFC circuitry and cognitive/emotional processing mediated by these circuits. Rats received five AMPH (2 mg/kg) or saline injections (controls) over 10 d, followed by 2-4 week drug washout. In vivo neurophysiological extracellular recordings in urethane-anesthetized rats were used to obtain data from mPFC neurons that were either inhibited or excited by BLA stimulation. In controls, acute AMPH attenuated BLA-evoked inhibitory or excitatory responses; these effects were mimicked by selective D(2) or D(1) agonists, respectively. However, in AMPH-treated rats, the ability of these dopaminergic manipulations to modulate BLA-driven decreases/increases in mPFC activity was abolished. Repeated AMPH also blunted the excitatory effects of ventral tegmental area stimulation on mPFC neural firing. Behavioral studies assessed the effect of repeated AMPH on decision making with conditioned punishment, a process mediated by BLA-mPFC circuitry and mesocortical DA. These treatments impaired the ability of rats to use conditioned aversive stimuli (footshock-associated cue) to guide the direction of instrumental responding. Collectively, these data suggest that repeated AMPH exposure can lead to persistent disruption of dopaminergic modulation of BLA-mPFC circuitry, which may underlie impairments in cognitive/emotional processing observed in stimulant abusers. Furthermore, they suggest that impairments in decision making guided by aversive stimuli observed in stimulant abusers may be the result of repeated drug exposure.
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Yokobayashi E, Ujike H, Kotaka T, Okahisa Y, Takaki M, Kodama M, Inada T, Uchimura N, Yamada M, Iwata N, Iyo M, Sora I, Ozaki N, Kuroda S. Association study of serine racemase gene with methamphetamine psychosis. Curr Neuropharmacol 2011; 9:169-75. [PMID: 21886585 PMCID: PMC3137175 DOI: 10.2174/157015911795017092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 04/17/2010] [Accepted: 05/26/2010] [Indexed: 11/22/2022] Open
Abstract
Experimental studies have demonstrated that not only dopaminergic signaling but also glutamatergic/NMDA receptor signaling play indispensable roles in the development of methamphetamine psychosis. Our recent genetic studies provided evidence that genetic variants of glutamate-related genes such as DTNBP1, GLYT1, and G72, which are involved in glutamate release and regulation of co-agonists for NMDA receptors, conferred susceptibility to methamphetamine psychosis. Serine racemase converts l-serine to d-serine, which is an endogenous co-agonist for NMDA receptors. Three single nucleotide polymorphisms (SNPs) in the promoter region of the serine racemase gene (SRR), rs224770, rs3760229, and rs408067, were proven to affect the transcription activity of SRR. Therefore, we examined these SNPs in 225 patients with methamphetamine psychosis and 291 age- and sex-matched controls. There was no significant association between methamphetamine psychosis and any SNP examined or between the disorder and haplotypes comprising the three SNPs. However, rs408067 was significantly associated with the prognosis for methamphetamine psychosis and multi-substance abuse status. The patients with C-positive genotypes (CC or CG) of rs408067 showed better prognosis of psychosis after therapy and less abuse of multiple substances than the patients with GG genotypes. Because the C allele of rs408067 reduces the expression of SRR, a lower d-serine level or reduced NMDA receptor activation may affect the prognosis of methamphetamine psychosis and multiple substance abuse. Our sample size is, however, not large enough to eliminate the possibility of a type I error, our findings must be confirmed by replicate studies with larger samples.
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Affiliation(s)
- E Yokobayashi
- Department of Neuropsychiatry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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Steketee JD, Kalivas PW. Drug wanting: behavioral sensitization and relapse to drug-seeking behavior. Pharmacol Rev 2011; 63:348-65. [PMID: 21490129 DOI: 10.1124/pr.109.001933] [Citation(s) in RCA: 439] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Repeated exposure to drugs of abuse enhances the motor-stimulant response to these drugs, a phenomenon termed behavioral sensitization. Animals that are extinguished from self-administration training readily relapse to drug, conditioned cue, or stress priming. The involvement of sensitization in reinstated drug-seeking behavior remains controversial. This review describes sensitization and reinstated drug seeking as behavioral events, and the neural circuitry, neurochemistry, and neuropharmacology underlying both behavioral models will be described, compared, and contrasted. It seems that although sensitization and reinstatement involve overlapping circuitry and neurotransmitter and receptor systems, the role of sensitization in reinstatement remains ill-defined. Nevertheless, it is argued that sensitization remains a useful model for determining the neural basis of addiction, and an example is provided in which data from sensitization studies led to potential pharmacotherapies that have been tested in animal models of relapse and in human addicts.
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Affiliation(s)
- Jeffery D Steketee
- Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163, USA.
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Amphetamine exposure selectively enhances hippocampus-dependent spatial learning and attenuates amygdala-dependent cue learning. Neuropsychopharmacology 2010; 35:1440-52. [PMID: 20200510 PMCID: PMC3055464 DOI: 10.1038/npp.2010.14] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Behaviorally sensitizing regimen of amphetamine (AMPH) exposure has diverse effects on learning, memory, and cognition that are likely to be a consequence of long-term neural adaptations occurring in the cortico-limbic-striatal circuitry. In particular, altered dopamine signaling in the nucleus accumbens and medial prefrontal cortex has been implicated to underlie AMPH-induced changes in behavior. This study sought to test the hypothesis that repeated AMPH exposure disrupts the regulation of limbic information processing and the balance of competing limbic control over appetitive behavior. Mice received seven intraperitoneal injections of D-AMPH (2.5 mg/kg or 5 mg/kg) or vehicle solution (saline) and were trained in (1) a simultaneous conditioned cue and place preference task using a six-arm radial maze, found to depend on the integrity of the hippocampus (HPC) and basolateral amygdala (BLA), respectively and (2) a conditional BLA-dependent cue, and HPC-dependent place learning task using an elevated T-maze. In both tasks, the vehicle pretreatment group initially acquired cue learning, followed by the emergence of significant place/spatial learning. In contrast, pretreatment with repeated AMPH caused marked deviations from normal acquisition patterns of place and cue conditioning, significantly facilitating HPC-dependent place conditioning in the first task while attenuating BLA-dependent cue conditioning in both tasks. These findings provide the first demonstration of an aberrant regulation of HPC- and BLA-dependent learning as a result of AMPH exposure, highlighting the importance of the meso-coticolimbic dopamine system in maintaining the balance of limbic control over appetitive behavior.
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Gulley JM, Stanis JJ. Adaptations in medial prefrontal cortex function associated with amphetamine-induced behavioral sensitization. Neuroscience 2009; 166:615-24. [PMID: 20035836 DOI: 10.1016/j.neuroscience.2009.12.044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 12/15/2009] [Accepted: 12/17/2009] [Indexed: 11/25/2022]
Abstract
Neuroadaptations in the prefrontal cortex (PFC) are hypothesized to play an important role in the behavioral changes associated with repeated psychostimulant exposure, but there are few published studies that measure neuronal activity during the development and expression of sensitization. To address this, we recorded single neuron activity in the medial PFC (mPFC) of male rats that were exposed for 5 days to saline or amphetamine (AMPH; 1.0 mg/kg i.p.) and then given saline or AMPH challenges following a three-day withdrawal. We found that rats exposed to AMPH developed locomotor sensitization to the drug that emerged on the fifth treatment session and became statistically significant at AMPH challenge. This was associated with no change in baseline (i.e., pre-injection) activity of mPFC neurons across the treatment or challenge sessions. Following the first AMPH injection, mPFC neurons responded primarily with reductions in firing, with the overall pattern and magnitude of responses remaining largely similar following repeated treatment. The exception was in the minority of cells that respond to AMPH with increases in firing rate. In this population, the magnitude of excitations peaked during the fifth AMPH exposure and was still relatively elevated at the AMPH challenge. Furthermore, these units increased firing during a saline challenge that was given to assess associative conditioning. These results suggest that AMPH-induced adaptations in mPFC function are not as apparent as AMPH-induced adaptations in behavior. When mPFC adaptations do occur, they appear limited to the population of neurons that increase their firing in response to AMPH.
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Affiliation(s)
- J M Gulley
- Department of Psychology and Neuroscience Program, University of Illinois at Urbana-Champaign, 731 Psychology Building MC-716, 603 E Daniel Street, Champaign, IL 61820, USA.
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The amphetamine sensitization model of schizophrenia: relevance beyond psychotic symptoms? Psychopharmacology (Berl) 2009; 206:603-21. [PMID: 19326100 DOI: 10.1007/s00213-009-1514-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 03/10/2009] [Indexed: 10/21/2022]
Abstract
RATIONALE A sensitized dopamine system may be linked to the genesis of psychotic symptoms in schizophrenia. Following withdrawal from amphetamine exposures, psychotic-like traits have been robustly demonstrated, but the presence of cognitive/mnemonic deficits remains uncertain. METHODS Adult male Lewis and Fischer rats, differing in cognitive performance, were exposed intermittently to escalating doses of amphetamine over 5 weeks. This was effective in producing behavioral sensitization to a subsequent amphetamine challenge. Following 27 days of drug withdrawal, the animals were assessed in Pavlovian conditioning, object recognition, and spatial working memory. In addition, prepulse inhibition (PPI), spontaneous motor activity, and anxiety-like behavior were measured. RESULTS Amphetamine pretreatment induced behavioral sensitization in both rat strains similarly. Working memory was enhanced in Fischer but not Lewis rats following withdrawal. Spontaneous novel object preference was enhanced in sensitized Fischer rats, but was impaired in sensitized Lewis rats, thus effectively reversing the strain difference in non-sensitized controls. In contrast, Pavlovian fear conditioning remained unaffected and so were anxiety-like behavior, open field activity, and PPI. CONCLUSION The face validity of the amphetamine withdrawal model for cognitive deficits was limited to the object recognition memory impairment observed in sensitized Lewis rats. Yet, the possibility that enhancing dopaminergic neurotransmission may facilitate object recognition and spatial working memory performance was demonstrated in sensitized Fischer rats. Identification of the mechanisms underlying such strain-dependent effects would be instrumental in the further specifications of the construct validity, and therefore the limitations and potential of the amphetamine sensitization model of schizophrenia.
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Perturbations in different forms of cost/benefit decision making induced by repeated amphetamine exposure. Psychopharmacology (Berl) 2009; 205:189-201. [PMID: 19365622 DOI: 10.1007/s00213-009-1529-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 03/22/2009] [Indexed: 10/20/2022]
Abstract
RATIONALE Psychostimulant abuse has been linked to impairments in cost-benefit decision making. OBJECTIVE We assessed the effects of repeated amphetamine (AMPH) treatment in rodents on two distinct forms of decision making. MATERIALS AND METHODS Separate groups of rats were trained for 26 days on either a probabilistic (risk) or effort-discounting task, each consisting of four discrete blocks of ten choice trials. One lever always delivered a smaller reward (one or two pellets), whereas another lever delivered a four-pellet reward. For risk-discounting, the probability of receiving the larger reward decreased across trial blocks (100-12.5%), whereas on the effort task, four pellets could be obtained after a ratio of presses that increased across blocks (2-20). After training, rats received 15 saline or AMPH injections (escalating from 1 to 5 mg/kg) and were then retested during acute and long-term withdrawal. RESULTS Repeated AMPH administration increased risky choice 2-3 weeks after drug exposure, whereas these treatments did not alter effort-based decision making in a separate group of animals. However, prior AMPH exposure sensitized the effects of acute AMPH on both forms of decision making, whereby lower doses were effective at inducing "risky" and "lazy" patterns of choice. CONCLUSIONS Repeated AMPH exposure leads to relatively long-lasting increases in risky choice, as well as sensitization to the effects of acute AMPH on different forms of cost/benefit decision making. These findings suggest that maladaptive decision-making processes exhibited by psychostimulant abusers may be caused in part by repeated drug exposure.
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Morshedi MM, Rademacher DJ, Meredith GE. Increased synapses in the medial prefrontal cortex are associated with repeated amphetamine administration. Synapse 2009; 63:126-35. [PMID: 19016489 DOI: 10.1002/syn.20591] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Psychostimulant drug experience leads not only to long-lasting changes in behavior but also modifications in the activity and morphology of pyramidal neurons in the medial prefrontal cortex (mPFC). The objective of this study was to establish whether repeated treatment of rats with amphetamine (AMPH) is accompanied by changes in the pattern or types of synapses in the mPFC and, specifically, onto neurons that project to the lateral hypothalamus, where our earlier work has shown increased markers of neuronal activity after repeated AMPH treatment (Morshedi and Meredith [2008] Psychopharmacology (Berl) 197:179-189). Rats were treated with a behaviorally sensitizing regimen of AMPH, following which synapses in the infralimbic and prelimbic cortices of the mPFC, were analyzed with unbiased stereology (physical disector and electron microscopy). All synapses were counted and their targets were identified by standard methodological criteria. Repeated AMPH administration was associated with a significant increase in the number of asymmetric axospinous synapses, no change in axodendritic or axosomatic contacts, and no change in the total number of synapses on corticolateral hypothalamic pyramidal neurons compared to vehicle-treated rats. Therefore, behavioral sensitization as a result of repeated exposure to AMPH is accompanied by the increased formation of spine, but not dendritic, synapses onto pyramidal neurons in the mPFC.
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Affiliation(s)
- Maud M Morshedi
- Department of Cellular and Molecular Pharmacology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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17
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Nelson CL, Milovanovic M, Wetter JB, Ford KA, Wolf ME. Behavioral sensitization to amphetamine is not accompanied by changes in glutamate receptor surface expression in the rat nucleus accumbens. J Neurochem 2009; 109:35-51. [PMID: 19183251 DOI: 10.1111/j.1471-4159.2009.05911.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We examined whether behavioral sensitization to amphetamine is associated with redistribution of glutamate receptors (GluR) in the rat nucleus accumbens (NAc) or dorsolateral striatum (DLSTR). Following repeated amphetamine treatment and 21 days of withdrawal, surface and intracellular levels of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) or NMDA receptor subunits were determined using a protein cross-linking assay. In contrast to our previous results in cocaine-sensitized rats, we did not observe redistribution of GluR1 or GluR2 to the cell surface in the NAc after amphetamine withdrawal, although a small increase in total GluR1 was found in the shell subregion. Nor did we observe activation of signaling pathways associated with cocaine-induced AMPA receptor trafficking or changes in NMDA receptor subunits. No significant changes were observed in the DLSTR. We also investigated the effect of administering a challenge injection of amphetamine to amphetamine-sensitized rats 24 h prior to biochemical analysis based on prior studies showing that cocaine challenge decreases AMPA receptor surface expression in the NAc of cocaine-sensitized rats. GluR1 and GluR2 were not significantly altered in either NAc or DLSTR, although a modest effect on GluR3 cannot be ruled out. Our results suggest that glutamate transmission in the NAc is dramatically different in rats sensitized to amphetamine versus cocaine.
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Affiliation(s)
- Christopher L Nelson
- Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064-3095, USA
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18
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Repeated amphetamine administration induces Fos in prefrontal cortical neurons that project to the lateral hypothalamus but not the nucleus accumbens or basolateral amygdala. Psychopharmacology (Berl) 2008; 197:179-89. [PMID: 18080115 PMCID: PMC2553393 DOI: 10.1007/s00213-007-1021-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 11/09/2007] [Indexed: 02/04/2023]
Abstract
RATIONALE The development of sensitization to amphetamine (AMPH) is dependent on increases in excitatory outflow from the medial prefrontal cortex (mPFC) to subcortical centers. These projections are clearly important for the progressive enhancement of the behavioral response during drug administration that persists through withdrawal. OBJECTIVES The objective of this study was to identify the mPFC subcortical pathway(s) activated by a sensitizing regimen of AMPH. MATERIALS AND METHODS Using retrograde labeling techniques, Fos activation was evaluated in the predominant projection pathways of the mPFC of sensitized rats after a challenge injection of AMPH. RESULTS There was a significant increase in Fos-immunoreactive cells in the mPFC, nucleus accumbens (NAc), basolateral amygdala (BLA), and lateral hypothalamus (LH) of rats treated repeatedly with AMPH when compared to vehicle-treated controls. The mPFC pyramidal neurons that project to the LH but not the NAc or BLA show a significant induction of Fos after repeated AMPH treatment. In addition, we found a dramatic increase in Fos-activated orexin neurons. CONCLUSIONS The LH, a region implicated in natural and drug reward processes, may play a role in the development and persistence of sensitization to repeated AMPH through its connections with the mPFC and possibly through its orexin neurons.
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19
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Gass JT, Olive MF. Glutamatergic substrates of drug addiction and alcoholism. Biochem Pharmacol 2008; 75:218-65. [PMID: 17706608 PMCID: PMC2239014 DOI: 10.1016/j.bcp.2007.06.039] [Citation(s) in RCA: 355] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 06/22/2007] [Accepted: 06/26/2007] [Indexed: 12/20/2022]
Abstract
The past two decades have witnessed a dramatic accumulation of evidence indicating that the excitatory amino acid glutamate plays an important role in drug addiction and alcoholism. The purpose of this review is to summarize findings on glutamatergic substrates of addiction, surveying data from both human and animal studies. The effects of various drugs of abuse on glutamatergic neurotransmission are discussed, as are the effects of pharmacological or genetic manipulation of various components of glutamate transmission on drug reinforcement, conditioned reward, extinction, and relapse-like behavior. In addition, glutamatergic agents that are currently in use or are undergoing testing in clinical trials for the treatment of addiction are discussed, including acamprosate, N-acetylcysteine, modafinil, topiramate, lamotrigine, gabapentin and memantine. All drugs of abuse appear to modulate glutamatergic transmission, albeit by different mechanisms, and this modulation of glutamate transmission is believed to result in long-lasting neuroplastic changes in the brain that may contribute to the perseveration of drug-seeking behavior and drug-associated memories. In general, attenuation of glutamatergic transmission reduces drug reward, reinforcement, and relapse-like behavior. On the other hand, potentiation of glutamatergic transmission appears to facilitate the extinction of drug-seeking behavior. However, attempts at identifying genetic polymorphisms in components of glutamate transmission in humans have yielded only a limited number of candidate genes that may serve as risk factors for the development of addiction. Nonetheless, manipulation of glutamatergic neurotransmission appears to be a promising avenue of research in developing improved therapeutic agents for the treatment of drug addiction and alcoholism.
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Affiliation(s)
- Justin T Gass
- Center for Drug and Alcohol Programs, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC 29425, USA
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20
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Featherstone RE, Kapur S, Fletcher PJ. The amphetamine-induced sensitized state as a model of schizophrenia. Prog Neuropsychopharmacol Biol Psychiatry 2007; 31:1556-71. [PMID: 17884274 DOI: 10.1016/j.pnpbp.2007.08.025] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Schizophrenia is a serious psychiatric disorder which impacts a broad range of cognitive, behavioural and emotional domains. In animals, exposure to an intermittent, escalating dose regimen of amphetamine induces a sensitized state that appears to share a number of behavioural and neurochemical similarities with schizophrenia. In humans repeated exposure to amphetamine, or other psychomotor stimulants, can induce sensitization as well as psychosis. The following paper evaluates the evidence for the amphetamine-induced sensitized state as an animal model of schizophrenia, focussing separately on the positive, cognitive and negative symptoms associated with this disease. Current evidence supports the use of amphetamine sensitization as a model of the positive symptoms observed in schizophrenia. Additionally, there is increasing evidence for long-lasting cognitive deficits in sensitized animals, especially in the area of attention and/or cognitive flexibility. Other areas of cognition, such as long-term memory, appear to be unaltered in sensitized animals. Finally, little evidence currently exists to either support or refute the use of amphetamine sensitization as a model of negative symptoms. It is concluded that amphetamine sensitization likely impacts behaviour by altering the functioning of mesolimbic dopamine systems and prefrontal cortical function and can serve as a model of certain domains of schizophrenia.
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Affiliation(s)
- R E Featherstone
- Section of Biopsychology, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, Canada M5T 1R8.
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21
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Morshedi MM, Meredith GE. Differential laminar effects of amphetamine on prefrontal parvalbumin interneurons. Neuroscience 2007; 149:617-24. [PMID: 17931790 DOI: 10.1016/j.neuroscience.2007.07.047] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 07/01/2007] [Accepted: 07/19/2007] [Indexed: 11/18/2022]
Abstract
The increase in excitatory outflow from the medial prefrontal cortex is critical to the development of sensitization to amphetamine. There is evidence that psychostimulant-induced changes in dopamine-GABA interactions are key to understanding the behaviorally sensitized response. The objective of this study was to characterize the effects of different amphetamine paradigms on the Fos activation of GABAergic interneurons that contain parvalbumin in the medial prefrontal cortex. Although a sensitizing, repeated regimen of amphetamine induced Fos in all cortical layers, only layer V parvalbumin-immunolabeled cells were activated in the infralimbic and prelimbic cortices. Repeated amphetamine treatment was also associated with a loss of parvalbumin immunoreactivity in layer V, but only in the prelimbic cortex. An acute amphetamine injection to naive rats was associated with an increase in Fos, but in parvalbumin-positive neurons of the prelimbic cortex, where it was preferentially induced in layer III. These data indicate that distinct substrates mediate the response to repeated or acute amphetamine treatment. They also suggest that a sensitizing amphetamine regimen directs medial prefrontal cortex (mPFC) outflow, via changes in inhibitory neuron activation, toward subcortical centers important in reward.
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Affiliation(s)
- M M Morshedi
- Department of Cellular and Molecular Pharmacology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA.
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22
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Fletcher PJ, Tenn CC, Sinyard J, Rizos Z, Kapur S. A sensitizing regimen of amphetamine impairs visual attention in the 5-choice serial reaction time test: reversal by a D1 receptor agonist injected into the medial prefrontal cortex. Neuropsychopharmacology 2007; 32:1122-32. [PMID: 17047670 DOI: 10.1038/sj.npp.1301221] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Exposure to repeated, intermittent, escalating doses of amphetamine in rats disrupts information processing in several tasks. Some of these deficits, notably impaired attentional set shifting, may reflect altered prefrontal cortex function. This study examined the effects of repeated treatment with amphetamine on performance in the 5-choice serial reaction time test. This test measures sustained visual attention, a behavior that is known to require the prefrontal cortex. Rats were trained to respond to a brief light stimulus presented randomly in one of five spatial locations, with 100 trials per session. Once performance had stabilized rats were treated with escalating doses of amphetamine (three injections per week for 5 weeks at 1-5 mg/kg per week); testing was continued on nondrug days, and for several weeks of withdrawal. During the amphetamine-treatment and withdrawal phases accuracy of responding was unaffected, but errors of omission increased. Lengthening the stimulus duration abolished this effect. Reducing the stimulus duration also reduced response accuracy and this effect was more marked in amphetamine-treated rats. Both reduced accuracy, and increased omissions, seen in amphetamine-treated rats were reversed by injecting the D1 receptor agonist SKF38393 into the medial prefrontal cortex. This treatment also prevented the decline in accuracy in control animals that resulted from reducing the stimulus duration. These results, indicating that exposure to amphetamine induces a long-lasting deficit in visual attention, add to a growing list of deficits suggesting that amphetamine-sensitized state may model the cognitive deficit state in schizophrenia. The reversal of these deficits by a D1 receptor agonist provides further evidence that prefrontal D1 dopamine receptors are involved in cognition, and may be a potential target for treatment of impaired cognition in schizophrenia.
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Affiliation(s)
- Paul J Fletcher
- Section of Biopsychology, Centre for Addiction and Mental Health, Toronto, ON, Canada.
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23
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Yamamoto H, Imai K, Kamegaya E, Takamatsu Y, Irago M, Hagino Y, Kasai S, Shimada K, Yamamoto T, Sora I, Koga H, Ikeda K. Repeated methamphetamine administration alters expression of the NMDA receptor channel epsilon2 subunit and kinesins in the mouse brain. Ann N Y Acad Sci 2007; 1074:97-103. [PMID: 17105907 DOI: 10.1196/annals.1369.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Repeated amphetamine administration results in behavioral sensitization. Behavioral sensitization related to abuse and/or relapse may be associated with stable changes in gene expression. To explore the participating genes, we examined the changes in gene expression levels 24 h or 21 days (long-term withdrawal period) after chronic methamphetamine (METH) treatment for 2 weeks. The expression of several genes related to glutamatergic neural transmission was altered, although changes in the corresponding protein expression were not always consistent with the results for mRNA expression. Of interest, in the frontal cortex of mice treated with METH for 2 weeks, protein expression levels of KIF17 and the N-methyl-D-asparate (NMDA) receptor channel epsilon2 subunit (NRepsilon2) were concomitantly increased. The alteration in expression of these proteins, KIF17 and NRepsilon2, might be a part of the molecular basis of the behavioral sensitization to METH.
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Affiliation(s)
- Hideko Yamamoto
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo 156-8585, Japan.
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24
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Mair RD, Kauer JA. Amphetamine depresses excitatory synaptic transmission at prefrontal cortical layer V synapses. Neuropharmacology 2007; 52:193-9. [PMID: 16895728 DOI: 10.1016/j.neuropharm.2006.07.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 06/30/2006] [Accepted: 07/03/2006] [Indexed: 11/24/2022]
Abstract
Dopamine modulates the function of glutamatergic synapses in prefrontal cortex, modifying synaptic strength and influencing synaptic plasticity. Here we have explored the ability of endogenous dopamine, present in slices containing the prefrontal cortex, to influence excitatory synaptic transmission. We found that 10 microM amphetamine, which releases and blocks the reuptake of dopamine from dopaminergic nerve terminals, significantly depressed excitatory field potentials recorded in layer V during stimulation of layer II/III. The depression was reversible, dose dependent and correlated with increased paired pulse facilitation, suggesting that amphetamine inhibits the presynaptic release of glutamate. Pharmacological dissection of this response showed that dopamine D1 receptors are likely to mediate the effects of endogenous dopamine on excitatory synaptic transmission, with little effect of alpha2 adrenergic receptors, serotonin receptors, or D2 dopamine receptors. The time to peak amphetamine effect was longer than expected based on diffusion, suggesting that to raise dopamine levels in brain slices amphetamine may need to be transported into the presynaptic terminals. These results provide evidence that D1/D5 receptors depress glutamate release at this cortical synapse, and suggest that amphetamine will have profound and persistent effects on PFC functioning in vivo. Dysregulation of this mechanism could contribute to the impairment in cognitive performance associated with abnormal PFC dopamine receptor activation.
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Affiliation(s)
- Robert D Mair
- Department of Molecular Pharmacology, Physiology and Biotechnology, Box G-B4, Brown University, Providence, RI 02912, USA
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25
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Lin SK, Pan WHT, Yeh PH. Prefrontal dopamine efflux during exposure to drug-associated contextual cues in rats with prior repeated methamphetamine. Brain Res Bull 2007; 71:365-71. [PMID: 17208653 DOI: 10.1016/j.brainresbull.2006.10.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 09/29/2006] [Accepted: 10/03/2006] [Indexed: 11/29/2022]
Abstract
Conditioned stimulus-reward response and prefrontal dopamine efflux under context previously paired with methamphetamine administration were assessed in rats with or without prior sensitizing regimen. Sensitizing pretreatment was administered with methamphetamine (1mg/kg, every other day for six sessions) for behavioral sensitization. The animals received methamphetamine (1mg/kg) or saline injection (each for six sessions) to pair with distinct contexts on alternate days to induce conditioned place preference. Then, dopamine outflows in the medial prefrontal cortex were analyzed on the next day via microdialysis study as animals exposed to the methamphetamine or saline-paired context, respectively. Prefrontal DA efflux increased in those rats without sensitizing pretreatment, while they occupied the methamphetamine-paired chamber. The rats with prior sensitizing regimen demonstrated more robust conditioned place preference than those without pretreatment, however, their dopamine efflux was attenuated, while remaining in methamphetamine-paired context. It is suggested that the attenuated responsiveness of mesocortical dopamine transmission in prior sensitized rats may, at least in part, be responsible for their augmented conditioned place preference, which resulted from activation of related brain areas that together strengthen the associative learning to drug-related stimuli. This paradigm may reflect a dysregulated prefrontal function in the methamphetamine abusers.
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Affiliation(s)
- Shi-Kwang Lin
- Institute of Pharmacology, National Yang-Ming University, 155, Section 2 Li-Noon Street, Taipei 112, Taiwan, ROC
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26
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Napier TC, Istre ED. Methamphetamine-induced sensitization includes a functional upregulation of ventral pallidal 5-HT2A/2C receptors. Synapse 2007; 62:14-21. [DOI: 10.1002/syn.20460] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Nogueira L, Kalivas PW, Lavin A. Long-term neuroadaptations produced by withdrawal from repeated cocaine treatment: role of dopaminergic receptors in modulating cortical excitability. J Neurosci 2006; 26:12308-13. [PMID: 17122056 PMCID: PMC5509070 DOI: 10.1523/jneurosci.3206-06.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Dopamine (DA) modulates neuronal activity in the prefrontal cortex (PFC) and is necessary for optimal cognitive function. Dopamine transmission in the PFC is also important for the behavioral adaptations produced by repeated exposure to cocaine. Therefore, we investigated the effects of repeated cocaine treatment followed by withdrawal (2-4 weeks) on the responsivity of cortical cells to electrical stimulation of the ventral tegmental area (VTA) and to systemic administration of DA D1 or D2 receptor antagonists. Cortical cells in cocaine- and saline-treated animals exhibited a similar decrease in excitability after the administration of D1 receptor antagonists. In contrast, cortical neurons from cocaine-treated rats exhibited a lack of D2-mediated regulation relative to saline rats. Furthermore, in contrast to saline-treated animals, VTA stimulation did not increase cortical excitability in the cocaine group. These data suggest that withdrawal from repeated cocaine administration elicits some long-term neuroadaptations in the PFC, including (1) reduced D2-mediated regulation of cortical excitability, (2) reduced responsivity of cortical cells to phasic increases in DA, and (3) a trend toward an overall decrease in excitability of PFC neurons.
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Affiliation(s)
- Lourdes Nogueira
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Peter W. Kalivas
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Antonieta Lavin
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
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28
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Homayoun H, Moghaddam B. Progression of cellular adaptations in medial prefrontal and orbitofrontal cortex in response to repeated amphetamine. J Neurosci 2006; 26:8025-39. [PMID: 16885216 PMCID: PMC2954613 DOI: 10.1523/jneurosci.0842-06.2006] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent theories on addiction implicate adaptive changes in prefrontal cortex (PFC) neurons in reinforcing and psychotomimetic properties of psychostimulants, yet little is known about how neuronal responses to these drugs change over time. Here we describe electrophysiological evidence for a progressive and sustained change in the response of PFC neurons to amphetamine during repeated exposure. In spontaneously behaving rats and in rats engaged in an instrumental responding task, we followed the activity of medial PFC (mPFC) and orbitofrontal cortex (OFC) neurons during daily exposure to amphetamine and after a post-withdrawal challenge. Repeated amphetamine increased the number of responsive neurons and the magnitude of responses and modified spontaneous burst patterns. These changes were apparent after a few exposures to amphetamine, were amplified after withdrawal, and were region specific in that repeated amphetamine increasingly produced inhibitory responses in mPFC and excitatory responses in OFC. In behaviorally engaged animals, the gradual enhancement in mPFC inhibition and OFC overactivation correlated with a progressive impairment of instrumental responding. Furthermore, these changes were evident predominately in neurons that displayed phasic responses during task-related events. These rapid-onset and sustained cellular adaptations suggest that even limited exposure to psychostimulants may reduce the influence of mPFC neurons on behavior while at the same time exaggerating information encoded by OFC neurons.
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Affiliation(s)
- Houman Homayoun
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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29
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McDaid J, Graham MP, Napier TC. Methamphetamine-induced sensitization differentially alters pCREB and DeltaFosB throughout the limbic circuit of the mammalian brain. Mol Pharmacol 2006; 70:2064-74. [PMID: 16951039 DOI: 10.1124/mol.106.023051] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Enhancements in behavior that accompany repeated, intermittent administration of abused drugs (sensitization) endure long after drug administration has ceased. Such persistence reflects changes in intracellular signaling cascades and associated gene transcription factors in brain regions that are engaged by abused drugs. This process is not characterized for the most potent psychomotor stimulant, methamphetamine. Using motor behavior as an index of brain state in rats, we verified that five once-daily injections of 2.5 mg/kg methamphetamine induced behavioral sensitization that was demonstrated (expressed) 3 and 14 days later. Using immunoblot procedures, limbic brain regions implicated in behavioral sensitization were assayed for extracellular signal-regulated kinase and its phosphorylated form (pERK/ERK, a signal transduction kinase), cAMP response element binding protein and its phosphorylated form (pCREB/CREB, a constitutively expressed transcriptional regulator), and DeltaFosB (a long-lasting transcription factor). pERK, ERK, and CREB levels were not changed for any region assayed. In the ventral tegmental area, pCREB and DeltaFosB also were not changed. pCREB (activated CREB) was elevated in the frontal cortex at 3 days withdrawal, but not at 14 days. pCREB levels were decreased at 14 days withdrawal in the nucleus accumbens and ventral pallidum. Accumbal and pallidal levels of DeltaFosB were increased at 3 days withdrawal, and this increase persisted to 14 days in the pallidum. Thus, only the ventral pallidum showed changes in molecular processes that consistently correlated with motor sensitization, revealing that this region may be associated with this enduring behavioral phenotype initiated by methamphetamine. The present findings expand our understanding of the neuroanatomical and molecular substrates that may play a role in the persistence of druginduced sensitization.
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Affiliation(s)
- John McDaid
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago Medical Center, Maywood, Illinois, USA
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30
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Peterson JD, Wolf ME, White FJ. Repeated amphetamine administration decreases D1 dopamine receptor-mediated inhibition of voltage-gated sodium currents in the prefrontal cortex. J Neurosci 2006; 26:3164-8. [PMID: 16554467 PMCID: PMC6674091 DOI: 10.1523/jneurosci.2375-05.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Adaptations in dopamine (DA) transmission in the prefrontal cortex (PFC) are thought to be critical to the development and persistence of drug addiction. Our previous findings showed that medial PFC (mPFC) neurons in rats treated repeatedly with amphetamine exhibit a decreased inhibitory response to iontophoretically applied DA, demonstrating altered DA receptor transmission. To determine the role postsynaptic DA D1 receptors play in this effect, we used whole-cell patch-clamp recordings of acutely dissociated pyramidal mPFC neurons and inhibition of transient voltage-sensitive sodium current (INaT) as a measure of D1 receptor function. After 3 d of withdrawal, neurons recorded from amphetamine-treated rats (5 mg/kg for 5 d) demonstrated a significant decrease in whole-cell INaT density and in the ability of D1 receptor stimulation to inhibit INaT. Application of a protein kinase A (PKA) inhibitor blocked the ability of D1 receptor activation to inhibit INaT and increased the current density of both groups to similar values. These results suggest that repeated amphetamine exposure results in subsensitivity of the INaT to D1 receptor-mediated inhibition because of a possible increase in basal PKA activity. This adaptation may contribute to perseverative behaviors in animals that self-administer psychostimulants as well as compromised PFC-dependent behaviors in human addicts.
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Affiliation(s)
- Jayms D Peterson
- Department of Physiology, Northwestern University, Chicago, Illinois 60611, USA.
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31
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Cassidy CM, Quirion R, Srivastava LK. Blockade of presynaptic voltage-gated calcium channels in the medial prefrontal cortex of neonatal rats leads to post-pubertal alterations in locomotor behavior. Brain Res 2006; 1083:164-73. [PMID: 16546143 DOI: 10.1016/j.brainres.2006.01.118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 01/25/2006] [Accepted: 01/28/2006] [Indexed: 10/24/2022]
Abstract
Although the etiology of neurodevelopmental mental disorders remains obscure, converging lines of evidence using animal modeling suggest a critical role for activity-dependent neurodevelopmental processes during neonatal life. Here, we report the behavioral effects of a novel technique designed to induce targeted, transient disruption of activity-dependent processes in early development via reduction of calcium-mediated neurotransmitter release. We examined the post-pubertal behavioral effects of neonatal (postnatal day 7) medial prefrontal cortex infusion of either vehicle or N-type and P/Q-type presynaptic voltage-dependent calcium channel blockers (omega-conotoxins MVIIA and MVIIC respectively; 6.8 and 45 pmol infused respectively) in rat pups. In a test of amphetamine-induced behavioral sensitization, neonatal omega-conotoxin MVIIA treatment significantly increased locomotion following repeated amphetamine injections (1.5 mg/kg i.p.) and significantly decreased locomotion following repeated saline injections relative to animals treated neonatally with vehicle. However, there was no effect of conotoxin treatment on the long-term expression of amphetamine sensitization. Neonatal treatment with omega-conotoxins had no effect on the other behaviors assayed, namely, acoustic startle response, prepulse inhibition of startle, novelty- and amphetamine-induced (1.5 mg/kg i.p.) locomotion, and anxiety-like behavior in the elevated plus-maze. These data confirm that transient, region-specific disruption of synaptic transmission during early development can have long-term effects on behaviors relevant to neurodevelopmental mental disorders.
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MESH Headings
- Aging/physiology
- Amphetamine/pharmacology
- Animals
- Animals, Newborn
- Anxiety/metabolism
- Anxiety/physiopathology
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Calcium Channel Blockers/pharmacology
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels, N-Type/drug effects
- Calcium Channels, N-Type/metabolism
- Calcium Channels, P-Type/drug effects
- Calcium Channels, P-Type/metabolism
- Central Nervous System Stimulants
- Disease Models, Animal
- Drug Interactions/physiology
- Mental Disorders/metabolism
- Mental Disorders/physiopathology
- Motor Activity/drug effects
- Motor Activity/physiology
- Prefrontal Cortex/drug effects
- Prefrontal Cortex/growth & development
- Prefrontal Cortex/metabolism
- Presynaptic Terminals/drug effects
- Presynaptic Terminals/metabolism
- Rats
- Rats, Sprague-Dawley
- Reflex, Startle/drug effects
- Reflex, Startle/physiology
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Time
- omega-Conotoxins/pharmacology
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Affiliation(s)
- Clifford M Cassidy
- Departments of Psychiatry and Neurology and Neurosurgery, Douglas Hospital Research Centre, McGill University, 6875 LaSalle Boulevard, Verdun, Montreal, Quebec, Canada H4H 1R3
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Williams GV, Castner SA. Under the curve: Critical issues for elucidating D1 receptor function in working memory. Neuroscience 2006; 139:263-76. [PMID: 16310964 DOI: 10.1016/j.neuroscience.2005.09.028] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 08/30/2005] [Accepted: 09/06/2005] [Indexed: 11/17/2022]
Abstract
It has been postulated that spatial working memory operates optimally within a limited range of dopamine transmission and D1 dopamine receptor signaling in prefrontal cortex. Insufficiency in prefrontal dopamine, as in aging, and excessive transmission, as in acute stress, lead to impairments in working memory that can be ameliorated by D1 receptor agonist and antagonist treatment, respectively. Iontophoretic investigations of dopamine's influence on the cellular mechanisms of working memory have revealed that moderate D1 blockade can enhance memory fields in primate prefrontal pyramidal neurons while strong blockade abolishes them. The combined behavioral and physiological evidence indicates that there is a normal range of dopamine function in prefrontal cortex that can be described as an "inverted-U" relationship between dopamine transmission and the integrity of working memory. Both in vivo and in vitro studies have demonstrated a role for dopamine in promoting the excitability of prefrontal pyramidal cells and facilitating their N-methyl-d-aspartate inputs, while simultaneously restraining recurrent excitation and facilitating feedforward inhibition. This evidence indicates that there is a fine balance between the synergistic mechanisms of D1 modulation in working memory. Given the critical role of prefrontal function for cognition, it is not surprising that this balancing act is perturbed by both subtle genetic influences and environmental events. Further, there is evidence for an imbalance in these dopaminergic mechanisms in multiple neuropsychiatric disorders, particularly schizophrenia, and in related nonhuman primate models. Elucidating the orchestration of dopamine signaling in key nodes within prefrontal microcircuitry is therefore pivotal for understanding the influence of dopamine transmission on the dynamics of working memory. Here, we explore the hypothesis that the window of optimal dopamine signaling changes on a behavioral time-scale, dependent upon current cognitive demands and local neuronal activity as well as long-term alterations in signaling pathways and gene expression. If we look under the bell-shaped curve of prefrontal dopamine function, it is the relationship between neuromodulation and cognitive function that promises to bridge our knowledge between molecule and mind.
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Affiliation(s)
- G V Williams
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT 06511, USA.
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Brady AM, Glick SD, O'Donnell P. Selective disruption of nucleus accumbens gating mechanisms in rats behaviorally sensitized to methamphetamine. J Neurosci 2005; 25:6687-95. [PMID: 16014730 PMCID: PMC6725438 DOI: 10.1523/jneurosci.0643-05.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 06/07/2005] [Accepted: 06/09/2005] [Indexed: 11/21/2022] Open
Abstract
Behavioral sensitization of psychostimulant-induced locomotor activity in rats has been proposed as a model of addiction and is accompanied by neuroadaptations in the nucleus accumbens and related circuits. Here, we used in vivo intracellular recordings to examine electrophysiological properties of accumbens neurons from animals that did or did not exhibit behavioral sensitization after repeated methamphetamine (5.0 mg/kg; 5 d). Although spontaneous activity of accumbens neurons was virtually unchanged, multiple synaptic interactions controlling membrane potential states were disrupted in sensitized animals. For example, stimulation of the ventral tegmental area attenuated accumbens responses to prefrontal cortex activation in nonsensitized and saline-treated animals, but not in sensitized animals. Acute methamphetamine (0.5 mg/kg) abolished accumbens up and down states in nonsensitized and saline-treated animals, suggesting a disruption of normal information processing in this area. However, acute methamphetamine failed to affect this pattern in accumbens neurons from sensitized animals. These results suggest that both acute and repeated methamphetamine administration can disrupt synaptic interactions in the nucleus accumbens; however, the nature of these alterations depends critically on the extent of behavioral sensitization. It is speculated that the response to acute methamphetamine in nonsensitized and saline-treated animals may be functionally adaptive, whereas the neuroadaptations observed in sensitized animals may be maladaptive and detrimental to accumbens information processing.
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Affiliation(s)
- Anne Marie Brady
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA
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Williams JM, Steketee JD. Time-dependent effects of repeated cocaine administration on dopamine transmission in the medial prefrontal cortex. Neuropharmacology 2005; 48:51-61. [PMID: 15617727 DOI: 10.1016/j.neuropharm.2004.09.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2004] [Revised: 08/30/2004] [Accepted: 09/15/2004] [Indexed: 11/28/2022]
Abstract
The medial prefrontal cortex (mPFC) has been implicated in the development of behavioral sensitization, which is the progressive enhancement of locomotor activity that occurs with repeated administration of psychostimulants. Previous data suggest that mPFC dopamine (DA) transmission may be attenuated in cocaine-sensitized animals, but the onset and duration of this effect have not been investigated. After recovery from stereotaxic surgeries, animals were given four daily injections of saline (1 ml/kg, i.p.) or cocaine (15 mg/kg, i.p.) and were subsequently challenged with saline or cocaine after 1, 7 or 30 d of withdrawal, on which days in vivo microdialysis of the mPFC was conducted simultaneously with monitoring of locomotor activity. Compared to acutely administered controls, the results in cocaine-pretreated animals were as follows: 1d of withdrawal was associated with a significant attenuation in cocaine-induced locomotion and mPFC DA overflow; after 7d, behavioral sensitization was accompanied by a significant attenuation in cocaine-induced elevations in mPFC DA levels; 30 d of withdrawal led to the expression of sensitized behaviors paralleled by an augmentation in cocaine-induced mPFC DA. These data suggest that repeated cocaine produces temporally distinct behavioral effects associated with alterations in mPFC DA responsiveness to cocaine that may be involved in the development of behavioral sensitization.
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Affiliation(s)
- Jason M Williams
- Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163, USA
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McDaid J, Dallimore JE, Mackie AR, Mickiewicz AL, Napier TC. Cross-sensitization to morphine in cocaine-sensitized rats: behavioral assessments correlate with enhanced responding of ventral pallidal neurons to morphine and glutamate, with diminished effects of GABA. J Pharmacol Exp Ther 2005; 313:1182-93. [PMID: 15722402 DOI: 10.1124/jpet.105.084038] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Common neurobiological substrates contribute to the progressively increased behavioral effects (i.e., sensitization) that occur with repeated intermittent treatments of cocaine and morphine. Consequently, repeated exposure to cocaine can augment responding to morphine (termed cross-sensitization). Drug-induced sensitization in rats may model aspects of the dysfunction in motivation that are imposed by addiction. The ventral pallidum (VP) is involved in motivated behaviors and its function is altered by acute administration of cocaine and morphine, but the effects of repeated drug exposure remain unknown. Targeting this paucity, the present study evaluated electrophysiological changes in the VP of rats exposed to five once-daily cocaine treatments (15 mg/kg i.p.). This regimen also induced behavioral-sensitization that was expressed 3 days later when the rats received either an acute injection of cocaine (15 mg/kg i.p.) or morphine (10 mg/kg i.p.). VP neurons recorded in vivo 3 days after the repeated cocaine treatment regimen demonstrated increased excitatory responding to microiontophoretic applications of morphine and glutamate. The maximal effect (E(max)) was increased without altering potency, suggesting a change in the functional efficacy of the respective receptor systems. This did not represent a potentiation in transmission in general, for the effects of GABA were diminished. The results provide the first evidence for cellular adaptation in the VP after a sensitizing drug treatment paradigm and reveal that cross-sensitization of drug-induced behaviors temporally correlates with changes in VP neuronal responding. These findings advance an emerging theme that alterations in the VP may contribute to the increased motivation for drug seeking that occurs in drug-withdrawn addicts.
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Affiliation(s)
- J McDaid
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, School of Medicine, Maywood, IL 60153-5515, USA
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Nasif FJ, Sidiropoulou K, Hu XT, White FJ. Repeated cocaine administration increases membrane excitability of pyramidal neurons in the rat medial prefrontal cortex. J Pharmacol Exp Ther 2004; 312:1305-13. [PMID: 15574686 DOI: 10.1124/jpet.104.075184] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Although the medial prefrontal cortex (mPFC) plays a critical role in cocaine addiction, the effects of chronic cocaine on mPFC neurons remain poorly understood. Here, we performed visualized current-clamp recordings to determine the effects of repeated cocaine administration on the membrane excitability of mPFC pyramidal neurons in rat brain slices. Following repeated cocaine administration (15 mg/kg/day i.p. for 5 days) with a 3-day withdrawal, alterations in membrane properties, including increased input resistance, reduced intensity of intracellular injected currents required for generation of Na(+)-dependent spikes (rheobase), and an increased number of spikes evoked by depolarizing current pulses were observed in mPFC neurons. The current-voltage relationship was also altered in cocaine-pretreated neurons showing reduced outward rectification during membrane depolarization and decreased inward rectification during membrane hyperpolarization. Application of the K(+) channel blocker Ba(2+) depolarized the resting membrane potential (RMP) and enhanced membrane potential response to injection of hyperpolarizing current pulses. However, the effects of Ba(2+) on RMP and hyperpolarized membrane potentials were significantly attenuated in cocaine-withdrawn neurons compared with saline-pretreated cells. These findings indicate that repeated cocaine administration increased the excitability of mPFC neurons after a short-term withdrawal, possibly via reducing the activity of the potassium inward rectifiers (K(ir)) and voltage-gated K(+) currents. Similar changes were also observed in cocaine-pretreated mPFC neurons after a long-term (2-3 weeks) withdrawal, revealing a persistent increase in excitability. These alterations in mPFC neuronal excitability may contribute to the development of behavioral sensitization and withdrawal effects following chronic cocaine exposure.
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Affiliation(s)
- Fernando J Nasif
- Department of Cellular and Molecular Pharmacology, Rosalind Franklin University of Medicine and Science, Chicago Medical School, 3333 Green Bay Road, North Chicago, Illinois 60064, USA
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Williams JM, Steketee JD. Cocaine increases medial prefrontal cortical glutamate overflow in cocaine-sensitized rats: a time course study. Eur J Neurosci 2004; 20:1639-46. [PMID: 15355331 DOI: 10.1111/j.1460-9568.2004.03618.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Excitatory amino acid transmission within mesocorticolimbic brain pathways is thought to play an important role in behavioural sensitization to psychomotor stimulants. The current studies evaluated a time course of the effects of cocaine on extracellular glutamate levels within the medial prefrontal cortex (mPFC) following increasing periods of withdrawal from repeated cocaine exposure. Male Sprague-Dawley rats underwent stereotaxic surgeries and were pretreated daily with saline (1 mL/kg/day x 4 days, i.p.) or cocaine (15 mg/kg/day x 4 days, i.p.) and withdrawn for 1, 7 or 30 days. After withdrawal rats were challenged with the same dose of saline or cocaine and in vivo microdialysis of the mPFC was conducted with concurrent analysis of locomotor activity. Animals that were withdrawn from repeated daily cocaine for 1 day and 7 days displayed an augmentation in cocaine-induced mPFC glutamate levels compared to saline and acute control subjects, which were similarly unaffected by cocaine challenge. At the 7 day time point, a subset of animals that received repeated cocaine did not express behavioural sensitization, nor did these animals exhibit the enhancement in mPFC glutamate in response to cocaine challenge. In contrast to these early effects, 30 days of withdrawal resulted in no significant changes in cocaine-induced mPFC glutamate levels regardless of the pretreatment or behavioural response. These data suggest that repeated cocaine administration transiently increases cocaine-induced glutamate levels in the mPFC during the first week of withdrawal, which may play an important role in the development of behavioural sensitization to cocaine.
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Affiliation(s)
- Jason M Williams
- Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163, USA.
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Wolf ME, Sun X, Mangiavacchi S, Chao SZ. Psychomotor stimulants and neuronal plasticity. Neuropharmacology 2004; 47 Suppl 1:61-79. [PMID: 15464126 DOI: 10.1016/j.neuropharm.2004.07.006] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Revised: 06/24/2004] [Accepted: 07/01/2004] [Indexed: 11/16/2022]
Abstract
Considerable evidence suggests that neuroadaptations leading to addiction involve the same glutamate-dependent cellular mechanisms that enable learning and memory. Long-term potentiation (LTP) and long-term depression (LTD) have therefore become an important focus of addiction research. This article reviews: (1) basic mechanisms underlying LTP and LTD, (2) the properties of LTP and LTD in ventral tegmental area, nucleus accumbens, dorsal striatum and prefrontal cortex, (3) studies demonstrating that psychomotor stimulants influence LTP or LTD in these brain regions. In addition, we discuss our recent work on cellular mechanisms by which dopamine may influence LTP and LTD. Based on evidence that AMPA receptors are inserted into synapses during LTP and removed during LTD, we investigated the effects of D1 receptor stimulation on AMPA receptor trafficking using primary cultures prepared from nucleus accumbens and prefrontal cortex. Our results suggest that activation of the D1 receptor-protein kinase A signaling pathway leads to externalization of AMPA receptors and promotes LTP. This provides a mechanism to explain facilitation of reward-related learning by dopamine. When this mechanism is activated in an unregulated manner by psychostimulants, maladaptive forms of neuroplasticity may occur that contribute to the transition from casual to compulsive drug use.
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Affiliation(s)
- Marina E Wolf
- Department of Neuroscience, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064-3095, USA.
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Abstract
Repeated administration of psychomotor stimulants may produce an impulsive state that could contribute to the cycle of drug abstinence and relapse seen in human drug addicts. We have previously reported that the inhibitory effects of dopamine (DA) on the firing rate of medial prefrontal cortex (mPFC) neurons were reduced in rats after repeated amphetamine treatment suggesting impaired mPFC DA function. Here, we used a differential reinforcement of low rates of responding (DRL) operant conditioning task, which is dependent on mPFC DA, to test impulsivity and inhibitory control. Food-restricted rats were trained to inhibit a nose poke response for 30s before a subsequent nose poke would result in a food reward (DRL 30). Once training was completed, rats received 5 days of no treatment, daily i.p. saline injections or daily i.p. injections of 5mg/kg amphetamine. Nine days of DRL 30 test performance began following a 3-day withdrawal from treatment. The percent of training active hole nose pokes was significantly increased and the percent of training efficiency was significantly decreased in rats withdrawn from repeated amphetamine administration as compared to saline or nai;ve rats. This suggests that impulsivity is increased during amphetamine withdrawal, which we hypothesize is associated with disrupted DA function in the mPFC.
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Affiliation(s)
- Jayms D Peterson
- Department of Neuroscience, Finch University of Health Sciences/The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064-3095, USA
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Stefani MR, Moghaddam B. Effects of repeated treatment with amphetamine or phencyclidine on working memory in the rat. Behav Brain Res 2002; 134:267-74. [PMID: 12191813 DOI: 10.1016/s0166-4328(02)00040-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Repeated exposure to psychomotor stimulants produces long-lasting molecular, cellular and locomotor behavioral changes. Such changes are likely to contribute to the development of drug addiction and psychosis. It is not clear whether these durable changes are accompanied by lasting changes in cognition. We examined the long-term effects of repeated treatment with phencyclidine (PCP) or amphetamine on working memory, using a discrete, paired-trials, delayed-alternation task sensitive to the acute effects of PCP and amphetamine, and to the integrity of the prefrontal cortex. Twice daily treatment with PCP (5.0 mg/kg) or amphetamine (2.5 mg/kg) for 5 days did not produce lasting, significant impairments in alternation performance in comparison to either pre-treatment baseline performance or to the vehicle-treated group. Subsequent challenge doses of PCP (1, 3 and 5 mg/kg) produced alternation deficits in vehicle, PCP, and amphetamine pre-treated groups that were dependent on dose, but not on pre-treatment regimen. However, rats pre-treated with PCP showed a trend towards sensitization in response to PCP challenge. The present data suggest that psychostimulant treatment regimens that are reported to produce long-lasting changes in neural morphology and locomotor behavior may not produce equally durable changes in working memory.
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Affiliation(s)
- Mark Renato Stefani
- Department of Psychiatry, Yale University School of Medicine, VA Medical Center, Mail Slot 116A/2, West Haven, CT 06516, USA.
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Lu W, Marinelli M, Xu D, Worley PF, Wolf ME. Amphetamine and cocaine do not increase Narp expression in rat ventral tegmental area, nucleus accumbens or prefrontal cortex, but Narp may contribute to individual differences in responding to a novel environment. Eur J Neurosci 2002; 15:2027-36. [PMID: 12099908 DOI: 10.1046/j.1460-9568.2002.02036.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Narp is an immediate early gene product that acts extracellularly to cluster AMPA receptors at excitatory synapses. The present study tested the hypothesis that drugs of abuse alter Narp expression and thereby influence AMPA receptor transmission in addiction-related circuits. Immunohistochemical studies demonstrated the existence of Narp-positive cells in hippocampus, prefrontal cortex (PFC) and nucleus accumbens (NAc), with lower levels of staining in the ventral tegmental area (VTA). To study the effects of psychomotor stimulants, Narp levels were quantified by Western blotting and normalized to actin. There were no differences in Narp levels in any brain region between rats treated with repeated saline injections, a single amphetamine injection (5 mg/kg), repeated amphetamine injections (5 mg/kg x 5 days), or repeated cocaine injections (20 mg/kg twice daily x 7 days). We also examined the possible role of Narp in individual differences in responding to a novel environment, a predictor of behavioural responses to psychomotor stimulant drugs including the propensity to acquire drug self-administration. Narp levels in the PFC, but not other regions, were significantly correlated with locomotor activity in a novel environment. These findings suggest that differential Narp expression in the PFC may be involved in determining individual vulnerability to drugs of abuse, perhaps by influencing the activity of its excitatory projections.
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Affiliation(s)
- W Lu
- Department of Neuroscience, The Chicago Medical School, North Chicago, IL 60064, USA
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