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Filipović D, Novak B, Xiao J, Yan Y, Bernardi RE, Turck CW. Chronic fluoxetine treatment in socially-isolated rats modulates the prefrontal cortex synaptoproteome. J Proteomics 2023; 282:104925. [PMID: 37164273 DOI: 10.1016/j.jprot.2023.104925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 05/01/2023] [Accepted: 05/03/2023] [Indexed: 05/12/2023]
Abstract
Exposure to chronic social isolation (CSIS) and synapse dysfunction have been implicated in the etiology of major depressive disorder (MDD). Fluoxetine (Flx) has been widely used to treat MDD, but its mechanisms of action remain elusive. We employed comparative synaptoproteomics to investigate the changes in the levels of proteins and molecular signaling pathways in prefrontal cortical samples of adult male Wistar rats exposed to CSIS, a rat model of depression, and CSIS rats treated with chronic Flx and controls, using liquid chromatography coupled to tandem mass spectrometry. Flx-treated control rats showed a decreased level of proteins involved in vesicle-mediated transport, and a predominantly increased level of exocytosis-associated proteins. CSIS significantly reduced the level of proteins involved in the ATP metabolic process, clathrin-dependent endocytosis, and proteolysis. Flx treatment in CSIS rats stimulated synaptic vesicle trafficking by increasing the regulation of exo/endocytosis-associated proteins, proteins involved in synaptic plasticity including neurogenesis, Cox5a, mitochondria-associated proteins involved in oxidative phosphorylation, and ion transport proteins (Slc8a2, Atp1b2). Flx treatment resulted in an increased synaptic vesicle dynamic, plasticity and mitochondrial functionality, and a suppression of CSIS-induced impairment of these processes. BIOLOGICAL SIGNIFICANCE: Identifying biomarkers of MDD and treatment response is the goal of many studies. Contemporary studies have shown that many molecular alterations associated with the pathophysiology of MDD reside within the synapse. As part of this research, a growing importance is the use of proteomics, as monitoring the changes in protein levels enables the identification of (possible) biochemical pathways and processes of importance for the development of depressive-like behavior and the efficacy of antidepressant treatments. We profiled proteomic changes representative of the development of CSIS-induced depressive-like behavior and the antidepressant effects of Flx. Our study has identified synaptosomal proteins and altered molecular pathways that may be potential markers of prefrontal cortical synaptic dysfunction associated with depressive-like behavior, and further clarified the mechanisms of depressive-like behavior and mode of action of Flx. Our findings indicate potential PFC synaptic targets for antidepressant treatment.
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Affiliation(s)
- Dragana Filipović
- Department of Molecular Biology and Endocrinology, "VINČA", Institute of Nuclear Sciences - National Institute of thе Republic of Serbia, University of Belgrade, Belgrade, Serbia.
| | - Božidar Novak
- Proteomics and Biomarkers, Max Planck Institute of Psychiatry, Munich, Germany
| | - Jinqiu Xiao
- Proteomics and Biomarkers, Max Planck Institute of Psychiatry, Munich, Germany
| | - Yu Yan
- Proteomics and Biomarkers, Max Planck Institute of Psychiatry, Munich, Germany
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Christoph W Turck
- Proteomics and Biomarkers, Max Planck Institute of Psychiatry, Munich, Germany
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Affiliation(s)
- Akseli Graf
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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3
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Wei S, Li Y, Gong Q, Liang H, Bernardi RE, Liang J. Molecular chaperone heat shock protein 70 inhibitors suppress conditioned place preference induced by morphine exposure in male rats. Addict Biol 2022; 27:e13163. [PMID: 35470556 DOI: 10.1111/adb.13163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 01/21/2022] [Accepted: 02/10/2022] [Indexed: 11/29/2022]
Abstract
Previous studies have indicated a role for molecular chaperone heat shock protein 70 (Hsp70) in the development of behavioural sensitization to morphine in rodents, suggesting that Hsp70 expression following morphine exposure is involved in molecular changes that may underlie addiction vulnerability. The current study was carried out to investigate the role of Hsp70 in the positive reinforcing properties of morphine using conditioned place preference (CPP) in male rats. An unbiased CPP procedure of three phases (pre-conditioning: d1-d3; conditioning: d4-d6; and testing: d7) was used. During the conditioning phase, morphine injections (5 mg/kg, subcutaneously) were administered to induce significant place preference. To explore the effect of Hsp70 on the development and expression of morphine CPP, Hsp70 inhibitors (PES, KNK437 and methylene blue) were administered into the lateral ventricle prior to either morphine conditioning sessions or a morphine challenge on the test day. Furthermore, Hsp70 expression within the mesocorticolimbic system was measured after the treatment with KNK437, a transcriptional inhibitor. We found that PES and KNK437, respectively, injected intracerebroventricularly dose-dependently attenuated both the development and expression of morphine CPP. Methylene blue treatment demonstrated an attenuation of the development, but had no effect on the expression of morphine CPP. Following KNK437 treatment, Hsp70 expression was significantly inhibited in the shell of nucleus accumbens (NAc) during both the development and expression of morphine CPP. The findings suggest that Hsp70 in the NAc shell plays an important role in the reinforcing effects of morphine and may be involved in the development of morphine dependence.
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Affiliation(s)
- Shoupeng Wei
- Department of Pharmacology, School of Basic Medical Science Peking University Beijing P. R. China
- The Seventh Affiliated Hospital of Sun Yat‐sen University Shenzhen P. R. China
| | - Yu‐ling Li
- Department of Pharmacology, School of Basic Medical Science Peking University Beijing P. R. China
- Department of Pharmacy East Hospital, Tongji University School of Medicine Shanghai P. R. China
| | - Qi Gong
- Department of Pharmacology, School of Basic Medical Science Peking University Beijing P. R. China
| | - Hui Liang
- Department of Pharmacology, School of Basic Medical Science Peking University Beijing P. R. China
| | - Rick E. Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim University of Heidelberg Mannheim Germany
| | - Jian‐hui Liang
- Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences Peking University Beijing P. R. China
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Zhang J, Wang X, Bernardi RE, Ju J, Wei S, Gong Z. Activation of AMPA Receptors in the Lateral Habenula Produces Anxiolytic Effects in a Rat Model of Parkinson’s Disease. Front Pharmacol 2022; 13:821975. [PMID: 35145415 PMCID: PMC8822149 DOI: 10.3389/fphar.2022.821975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 01/07/2022] [Indexed: 11/21/2022] Open
Abstract
Background: Parkinson’s disease (PD) is commonly accompanied with anxiety disorder, however, the mechanisms underlying PD-mediated anxiety remain elusive. The lateral habenula (LHb) is a critical brain region that influences the activity of the monoaminergic system in the midbrain and consequently modulates anxiety. Most neurons in the LHb express AMPA receptors (AMPARs). The PD model for the pharmacological intervention of AMPA receptors was established by the unilateral lesion of the substantia nigra pars compacta (SNc) with 6-hydroxydopamine (6-OHDA). Methods: The AMPAR agonist (S)-AMPA and antagonist NBQX were microinjected into the LHb, respectively, to examine whether anxiety-like behaviors were altered in sham-operated and SNc-lesion rats, measured with the paradigms of the open-field test (OPT) and elevated plus maze (EPM). Furthermore, dopamine (DA) and 5-hydroxytryptamine (5-HT) levels in the basolateral amygdala (BLA) were measured using in vivo microdialysis immediately following the injections of (S)-AMPA and NBQX into the LHb. Results: Activation of LHb AMPA receptors by (S)-AMPA produced anxiolytic-like behaviors and enhanced the extracellular DA and 5-HT in the BLA. Conversely, NBQX induced anxiety-like effects and suppressed the extracellular DA and 5-HT in the BLA. In addition, the minimal doses inducing the effects in the SNc-lesion rats were lower than those in sham-operated rats. Conclusion: These findings suggest that the effects of AMPA receptors in the LHb on anxiety-like behaviors likely involve the extracellular levels of DA and 5-HT in the BLA. The present results may improve our understanding of the neuropathology and/or treatment of PD.
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Affiliation(s)
- Jin Zhang
- State Key Laboratory of Chemical Oncogenomics, Guangdong Provincial Key Laboratory of Chemical Genomics, Shenzhen Graduate School, Peking University, Shenzhen, China
| | - Xiaobing Wang
- Department of Anatomy, College of Preclinical Medicine, Dali University, Dali, China
| | - Rick E. Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg, Germany
| | - Jun Ju
- Brain Research Centre and Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Shoupeng Wei
- Tomas Lindahl Nobel Laureate Laboratory, Precision Medicine Research Centre, Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
- *Correspondence: Shoupeng Wei, ; Zhiting Gong,
| | - Zhiting Gong
- Department of Anatomy, College of Preclinical Medicine, Dali University, Dali, China
- *Correspondence: Shoupeng Wei, ; Zhiting Gong,
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Morella I, Pohořalá V, Calpe-López C, Brambilla R, Spanagel R, Bernardi RE. Nicotine self-administration and ERK signaling are altered in RasGRF2 knockout mice. Front Pharmacol 2022; 13:986566. [PMID: 36120353 PMCID: PMC9479000 DOI: 10.3389/fphar.2022.986566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/10/2022] [Indexed: 11/29/2022] Open
Abstract
Ras/Raf/MEK/ERK (Ras-ERK) signaling has been demonstrated to play a role in the effects of drugs of abuse such as cocaine and alcohol, but has not been extensively examined in nicotine-related reward behaviors. We examined the role of Ras Guanine Nucleotide Releasing Factor 2 (RasGRF2), an upstream mediator of the Ras-ERK signaling pathway, on nicotine self-administration (SA) in RasGRF2 KO and WT mice. We first demonstrated that acute nicotine exposure (0.4 mg/kg) resulted in an increase in phosphorylated ERK1/2 (pERK1/2) in the striatum, consistent with previous reports. We also demonstrated that increases in pERK1/2 resulting from acute (0.4 mg/kg) and repeated (0.4 mg/kg, 10 daily injections) exposure to nicotine in WT mice were not present in RasGRF2 KO mice, confirming that RasGRF2 at least partly regulates the activity of the Ras-ERK signaling pathway following nicotine exposure. We then performed intravenous nicotine SA (0.03 mg/kg/infusion for 10 days) in RasGRF2 KO and WT mice. Consistent with a previous report using cocaine SA, RasGRF2 KO mice demonstrated an increase in nicotine SA relative to WT controls. These findings suggest a role for RasGRF2 in the reinforcing effects of nicotine, and implicate the Ras-ERK signaling pathway as a common mediator of the response to drugs of abuse.
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Affiliation(s)
- Ilaria Morella
- Neuroscience and Mental Health Innovation Institute, Cardiff University, Cardiff, United Kingdom.,Division of Neuroscience, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Veronika Pohořalá
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Claudia Calpe-López
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Riccardo Brambilla
- Neuroscience and Mental Health Innovation Institute, Cardiff University, Cardiff, United Kingdom.,Division of Neuroscience, School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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Pohořalá V, Enkel T, Bartsch D, Spanagel R, Bernardi RE. Sign- and goal-tracking score does not correlate with addiction-like behavior following prolonged cocaine self-administration. Psychopharmacology (Berl) 2021; 238:2335-2346. [PMID: 33950271 PMCID: PMC8292273 DOI: 10.1007/s00213-021-05858-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 04/19/2021] [Indexed: 12/13/2022]
Abstract
RATIONALE In classical conditioning, sign-tracking reflects behavior directed toward a conditioned stimulus (CS) in expectation of a reward (unconditioned stimulus, US); in contrast, goal-tracking describes behavior directed toward the location of delivery of a US. As cues previously paired with drugs of abuse promote drug-seeking and drug-taking behavior in both animals and humans and thus contribute to the severity of substance abuse, sign-tracking may represent a maladaptive cue-focused behavior that may increase addiction vulnerability as compared to goal-tracking. Recent studies do, in fact, support this possibility. Previous work in this area has focused primarily on paradigms using relatively limited exposure to drug rather than extended drug intake. OBJECTIVES Here, we used the DSM-IV-based 3-criteria (3-CRIT) model and examined whether a relationship exists between sign- or goal-tracking phenotypes and the prevalence of criteria associated with addiction-like behavior following extended cocaine self-administration as measured in this model. METHODS Forty-six male Sprague Dawley rats underwent a Pavlovian conditioned approach (PCA) procedure and were characterized along a continuum as goal-trackers (GTs), intermediates (INTs), or sign-trackers (STs). The animals were subsequently trained to intravenous self-administer cocaine during 45 self-administration (SA) sessions and characterized for the 3 criteria outlined in the model: persistence of drug-seeking, motivation for cocaine-taking, and resistance to punishment. RESULTS We performed correlational analyses on the traits measured, finding no relationships between PCA score and addiction-like characteristics measured using the 3-CRIT model of addiction. However, STs showed significantly greater resistance to punishment than GTs. CONCLUSIONS Phenotyping along a continuum of PCA scores may not be a valid predictor for identifying vulnerability to the addiction-like behaviors examined using the 3-CRIT model. However, PCA phenotype may predict a single feature of the 3-CRIT model, resistance to punishment, among those rats classified as either STs or GTs.
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Affiliation(s)
- Veronika Pohořalá
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany
| | - Thomas Enkel
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany.
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Olevska A, Spanagel R, Bernardi RE. Impaired contextual fear conditioning in RasGRF2 mutant mice is likely Ras-ERK-dependent. Neurobiol Learn Mem 2021; 181:107435. [PMID: 33831510 DOI: 10.1016/j.nlm.2021.107435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 03/08/2021] [Accepted: 03/31/2021] [Indexed: 10/21/2022]
Abstract
Ras/Raf/MEK/ERK (Ras-ERK) signaling has been shown to play an important role in fear acquisition. However, little information is known regarding the mechanisms that contribute to the regulation of this pathway in terms of the learning of conditioned fears. Ras Guanine Nucleotide Releasing Factor 2 (RasGRF2) is one of two guanine nucleotide exchange factors (GEF) that regulates the Ras-ERK signaling pathway in a Ca2+-dependent manner via control of the cycling of Ras isoforms between an inactive and active state. Here we sought to determine the role of RasGRF2 on contextual fear conditioning in RasGRF2 knockout (KO) and their wild type (WT) counterparts. Male KO and WT mice underwent a single session of contextual fear conditioning (12 min, 4 unsignaled shocks), followed by either daily 12-min retention trials or the molecular analysis of Ras activation and pERK1/2 activity. KO mice showed an impaired acquisition of contextual fear, as demonstrated by reduced freezing during fear conditioning and 24-hr retention tests relative to WT mice. Ras analysis following fear conditioning demonstrated a reduction in Ras activation in the hippocampus as well as a reduction in pERK1/2 in the CA1 region of the hippocampus in KO mice, suggesting that the decrease in fear conditioning in KO mice is at least in part due to the impairment of Ras-ERK signaling in the hippocampus during learning. These data indicate a role for RasGRF2 in contextual fear conditioning in mice that may be Ras-ERK-dependent.
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Affiliation(s)
- Anastasia Olevska
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Mannheim, Germany.
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Pohořalá V, Enkel T, Bartsch D, Spanagel R, Bernardi RE. Correction to: Sign‑ and goal‑tracking score does not correlate with addiction‑like behavior following prolonged cocaine self‑administration. Psychopharmacology (Berl) 2021; 238:2347. [PMID: 34132838 PMCID: PMC8492560 DOI: 10.1007/s00213-021-05891-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Veronika Pohořalá
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany
| | - Thomas Enkel
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5, 68159, Mannheim, Germany.
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Pohořalá V, Enkel T, Bartsch D, Spanagel R, Bernardi RE. Comment on Flagel et al.: Sign-tracking as a predictor of addiction vulnerability. Psychopharmacology (Berl) 2021; 238:2665-2666. [PMID: 34324003 PMCID: PMC8373764 DOI: 10.1007/s00213-021-05928-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 07/06/2021] [Indexed: 10/29/2022]
Affiliation(s)
- Veronika Pohořalá
- grid.7700.00000 0001 2190 4373Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5 68159 Mannheim, Germany
| | - Thomas Enkel
- grid.7700.00000 0001 2190 4373Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Dusan Bartsch
- grid.7700.00000 0001 2190 4373Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Rainer Spanagel
- grid.7700.00000 0001 2190 4373Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5 68159 Mannheim, Germany
| | - Rick E. Bernardi
- grid.7700.00000 0001 2190 4373Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J5 68159 Mannheim, Germany
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Wei S, Li Y, Gong Q, Liang H, Liu Q, Bernardi RE, Zhang H, Chen F, Lawrence AJ, Liang J. Brucine N‐Oxide Reduces Ethanol Intake and Preference in Alcohol‐Preferring Male Fawn‐Hooded Rats. Alcohol Clin Exp Res 2020; 44:1321-1328. [PMID: 32343845 DOI: 10.1111/acer.14344] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 04/18/2020] [Indexed: 02/05/2023]
Affiliation(s)
- Shoupeng Wei
- From the Department of Pharmacology (SW, QG, HL, QL) School of Basic Medicine Sciences Peking University Beijing China
| | - Yu‐ling Li
- Department of Pharmacy (Y‐LL) East Hospital Tongji University School of Medicine Shanghai China
| | - Qi Gong
- From the Department of Pharmacology (SW, QG, HL, QL) School of Basic Medicine Sciences Peking University Beijing China
| | - Hui Liang
- From the Department of Pharmacology (SW, QG, HL, QL) School of Basic Medicine Sciences Peking University Beijing China
| | - Qing Liu
- From the Department of Pharmacology (SW, QG, HL, QL) School of Basic Medicine Sciences Peking University Beijing China
| | - Rick E. Bernardi
- Institute of Psychopharmacology (REB) Central Institute of Mental Health Medical Faculty Mannheim University of Heidelberg Mannheim Germany
| | - Han‐Ting Zhang
- Departments of Behavioral Medicine & Psychiatry and Physiology & Pharmacology (H‐TZ) West Virginia University Health Sciences Center Morgantown West Virginia
| | - Feng Chen
- The Florey Institute of Neuroscience and Mental Health (FC, AJL) University of Melbourne Parkville3010Victoria Australia
| | - Andrew J. Lawrence
- The Florey Institute of Neuroscience and Mental Health (FC, AJL) University of Melbourne Parkville3010Victoria Australia
| | - Jian‐hui Liang
- Department of Molecular and Cellular Pharmacology (J‐hL) School of Pharmaceutical Sciences Peking University Beijing China
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Bernardi RE, Olevska A, Morella I, Fasano S, Santos E, Brambilla R, Spanagel R. The Inhibition of RasGRF2, But Not RasGRF1, Alters Cocaine Reward in Mice. J Neurosci 2019; 39:6325-6338. [PMID: 31182637 PMCID: PMC6687905 DOI: 10.1523/jneurosci.1120-18.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 05/17/2019] [Accepted: 06/04/2019] [Indexed: 01/12/2023] Open
Abstract
Ras/Raf/MEK/ERK (Ras-ERK) signaling has been implicated in the effects of drugs of abuse. Inhibitors of MEK1/2, the kinases upstream of ERK1/2, have been critical in defining the role of the Ras-ERK cascade in drug-dependent alterations in behavioral plasticity, but the Ras family of small GTPases has not been extensively examined in drug-related behaviors. We examined the role of Ras Guanine Nucleotide Releasing Factor 1 (RasGRF1) and 2 (RasGRF2), upstream regulators of the Ras-ERK signaling cascade, on cocaine self-administration (SA) in male mice. We first established a role for Ras-ERK signaling in cocaine SA, demonstrating that pERK1/2 is upregulated following SA in C57BL/6N mice in striatum. We then compared RasGRF1 and RasGRF2 KO mouse lines, demonstrating that cocaine SA in RasGRF2 KO mice was increased relative to WT controls, whereas RasGRF1 KO and WT mice did not differ. This effect in RasGRF2 mice is likely mediated by the Ras-ERK signaling pathway, as pERK1/2 upregulation following cocaine SA was absent in RasGRF2 KO mice. Interestingly, the lentiviral knockdown of RasGRF2 in the NAc had the opposite effect to that in RasGRF2 KO mice, reducing cocaine SA. We subsequently demonstrated that the MEK inhibitor PD325901 administered peripherally prior to cocaine SA increased cocaine intake, replicating the increase seen in RasGRF2 KO mice, whereas PD325901 administered into the NAc decreased cocaine intake, similar to the effect seen following lentiviral knockdown of RasGRF2. These data indicate a role for RasGRF2 in cocaine SA in mice that is ERK-dependent, and suggest a differential effect of global versus site-specific RasGRF2 inhibition.SIGNIFICANCE STATEMENT Exposure to drugs of abuse activates a variety of intracellular pathways, and following repeated exposure, persistent changes in these pathways contribute to drug dependence. Downstream components of the Ras-ERK signaling cascade are involved in the acute and chronic effects of drugs of abuse, but their upstream mediators have not been extensively characterized. Here we show, using a combination of molecular, pharmacological, and lentiviral techniques, that the guanine nucleotide exchange factor RasGRF2 mediates cocaine self-administration via an ERK-dependent mechanism, whereas RasGRF1 has no effect on responding for cocaine. These data indicate dissociative effects of mediators of Ras activity on cocaine reward and expand the understanding of the contribution of Ras-ERK signaling to drug-taking behavior.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim 68159, Germany,
| | - Anastasia Olevska
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim 68159, Germany
| | - Ilaria Morella
- Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff CF24 4HQ, United Kingdom
- Cardiff University, School of Biosciences, Division of Neuroscience, Cardiff CF24 4HQ, United Kingdom, and
| | - Stefania Fasano
- Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff CF24 4HQ, United Kingdom
- Cardiff University, School of Biosciences, Division of Neuroscience, Cardiff CF24 4HQ, United Kingdom, and
| | - Eugenio Santos
- Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC-Universidad de Salamanca) and CIBERONC, Salamanca, Spain, 37007
| | - Riccardo Brambilla
- Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff CF24 4HQ, United Kingdom
- Cardiff University, School of Biosciences, Division of Neuroscience, Cardiff CF24 4HQ, United Kingdom, and
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim 68159, Germany
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Stanisavljević A, Perić I, Bernardi RE, Gass P, Filipović D. Clozapine increased c-Fos protein expression in several brain subregions of socially isolated rats. Brain Res Bull 2019; 152:35-44. [PMID: 31299320 DOI: 10.1016/j.brainresbull.2019.07.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 07/02/2019] [Accepted: 07/05/2019] [Indexed: 12/24/2022]
Abstract
Chronic social stress and/or pharmacological treatments differentially modulate the expression of c-Fos, a marker of neuronal activity, in subregions of the rat brain. Here, we examined the effect of the atypical antipsychotic Clozapine (Clz) (20 mg/kg/day for 3 weeks) on the neuronal activation pattern of c-Fos protein expression in stress-relevant brain subregions of adult male Wistar rats exposed to chronic social isolation (CSIS: 3 weeks), an animal model of depression and schizophrenia, and controls. The protein expression of c-Fos was also used to map neuronal populations in brain subregions activated by CSIS alone. Subregions which showed significantly increased c-Fos protein expression following CSIS included the retrosplenial cortex (RSC), (subregions:RSC granular cortex, c region (RSGc) and dysgranular (RSD)), dentate gyrus, dorsal (DGd), paraventricular thalamic nucleus, posterior part (PVP), lateral (LA)/basolateral (BL) complex of amygdala, caudate putamen (CPu) and accumbens nucleus, shell (AcbSh). Increases in c-Fos protein expression in the RSGc, RSD, DGd, PVP, LA/BL complex of amygdala and striatum (CPu, Acb Core (AcbC) and AcbSh) following Clz treatment in controls were found. Clz applied simultaneously with CSIS modulated neuronal activity in CPu, AcbC and AcbSh subregions compared to CSIS alone, increasing c-Fos protein expression. Furthermore, Clz revealed synergistic effects with CSIS in the CA1d and PVP. These identified neural circuits reflect brain subregions activated following CSIS and/or Clz administration. These data further contribute to the understanding of the effectiveness of Clz in the modulation of brain subregion activation in response to CSIS.
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Affiliation(s)
- Andrijana Stanisavljević
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, 11001 Belgrade, Serbia
| | - Ivana Perić
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, 11001 Belgrade, Serbia
| | - Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim 68159, Germany
| | - Peter Gass
- Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim 68159, Germany
| | - Dragana Filipović
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, 11001 Belgrade, Serbia.
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Baur K, Hach A, Bernardi RE, Spanagel R, Bading H, Bengtson CP. c-Fos marking of identified midbrain neurons coactive after nicotine administration in-vivo. J Comp Neurol 2018; 526:2019-2031. [PMID: 29888787 DOI: 10.1002/cne.24471] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 04/26/2018] [Accepted: 05/05/2018] [Indexed: 11/08/2022]
Abstract
Despite the reduced life expectancy and staggering financial burden of medical treatment associated with tobacco smoking, the molecular, cellular, and ensemble adaptations associated with chronic nicotine consumption remain poorly understood. Complex circuitry interconnecting dopaminergic and cholinergic regions of the midbrain and mesopontine tegmentum are critical for nicotine associated reward. Yet our knowledge of the nicotine activation of these regions is incomplete, in part due to their cell type diversity. We performed double immunohistochemistry for the immediate early gene and surrogate activity sensor, c-Fos, and markers for either cholinergic, dopaminergic or GABAergic cell types in mice treated with nicotine. Both acute (0.5 mg/kg) and chronic (0.5 mg/kg/day for 7 days) nicotine strongly activated GABAergic neurons of the interpeduncular nucleus and medial terminal nucleus of the accessory optic tract (MT). Acute but not chronic nicotine also activated small percentages of dopaminergic and other neurons in the ventral tegmental area (VTA) as well as noncholinergic neurons in the pedunculotegmental and laterodorsal tegmental nuclei (PTg/LDTg). Twenty four hours of nicotine withdrawal after chronic nicotine treatment suppressed c-Fos activation in the MT. In comparison to nicotine, a single dose of cocaine caused a similar activation in the PTg/LDTg but not the VTA where GABAergic cells were strongly activated but dopaminergic neurons were not affected. These results indicate the existence of drug of abuse specific ensembles. The loss of ensemble activation in the VTA and PTg/LDTg after chronic nicotine represents a molecular and cellular tolerance which may have implications for the mechanisms underlying nicotine dependence.
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Affiliation(s)
- Katja Baur
- Neurobiology, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - Arian Hach
- Neurobiology, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - Rick E Bernardi
- Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Heidelberg, Germany
| | - Rainer Spanagel
- Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, Heidelberg, Germany
| | - Hilmar Bading
- Neurobiology, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - C Peter Bengtson
- Neurobiology, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
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Bernardi RE, Broccoli L, Hirth N, Justice NJ, Deussing JM, Hansson AC, Spanagel R. Dissociable Role of Corticotropin Releasing Hormone Receptor Subtype 1 on Dopaminergic and D1 Dopaminoceptive Neurons in Cocaine Seeking Behavior. Front Behav Neurosci 2017; 11:221. [PMID: 29180955 PMCID: PMC5693884 DOI: 10.3389/fnbeh.2017.00221] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/24/2017] [Indexed: 11/18/2022] Open
Abstract
The ability of many drugs of abuse, including cocaine, to mediate reinforcement and drug-seeking behaviors is in part mediated by the corticotropin-releasing hormone (CRH) system, in which CRH exerts its effects partly via the CRH receptor subtype 1 (CRHR1) in extra-hypothalamic areas. In fact, CRHR1 expressed in regions of the mesolimbic dopamine (DA) system have been demonstrated to modify cocaine-induced DA release and alter cocaine-mediated behaviors. Here we examined the role of neuronal selectivity of CRHR1 within the mesolimbic system on cocaine-induced behaviors. First we used a transgenic mouse line expressing GFP under the control of the Crhr1 promoter for double fluorescence immunohistochemistry to demonstrate the cellular location of CRHR1 in both dopaminergic and D1 dopaminoceptive neurons. We then studied cocaine sensitization, self-administration, and reinstatement in inducible CRHR1 knockouts using the CreERT2/loxP in either dopamine transporter (DAT)-containing neurons (DAT-Crhr1) or dopamine receptor 1 (D1)-containing neurons (D1-Crhr1). For sensitization testing, mice received five daily injections of cocaine (15 mg/kg IP). For self-administration, mice received eight daily 2 h cocaine (0.5 mg/kg per infusion) self-administration sessions followed by extinction and reinstatement testing. There were no differences in the acute or sensitized locomotor response to cocaine in DAT-Crhr1 or D1-Crhr1 mice and their respective controls. Furthermore, both DAT-Crhr1 and D1-Crhr1 mice reliably self-administered cocaine at the level of controls. However, DAT-Crhr1 mice demonstrated a significant increase in cue-induced reinstatement relative to controls, whereas D1-Crhr1 mice demonstrated a significant decrease in cue-induced reinstatement relative to controls. These data demonstrate the involvement of CRHR1 in cue-induced reinstatement following cocaine self-administration, and implicate a bi-directional role of CRHR1 for cocaine craving.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Laura Broccoli
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Natalie Hirth
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Nicholas J Justice
- Institute of Molecular Medicine, University of Texas, Houston, TX, United States
| | - Jan M Deussing
- Molecular Neurogenetics, Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Munich, Germany
| | - Anita C Hansson
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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Bernardi RE, Zohsel K, Hirth N, Treutlein J, Heilig M, Laucht M, Spanagel R, Sommer WH. A gene-by-sex interaction for nicotine reward: evidence from humanized mice and epidemiology. Transl Psychiatry 2016; 6:e861. [PMID: 27459726 PMCID: PMC5545715 DOI: 10.1038/tp.2016.132] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 04/19/2016] [Accepted: 04/24/2016] [Indexed: 02/03/2023] Open
Abstract
It has been proposed that vulnerability to nicotine addiction is moderated by variation at the μ-opioid receptor locus (OPRM1), but results from human studies vary and prospective studies based on genotype are lacking. We have developed a humanized mouse model of the most common functional OPRM1 polymorphism rs1799971_A>G (A118G). Here we use this model system together with a cohort of German youth to examine the role of the OPRM1 A118G variation on nicotine reward. Nicotine reinforcement was examined in the humanized mouse model using i.v. self-administration. Male (n=17) and female (n=26) mice homozygous either for the major human A allele (AA) or the minor G allele (GG) underwent eight daily 2 h sessions of nicotine self-administration. Furthermore, male (n=104) and female (n=118) subjects homozygous for the A allele or carrying the G allele from the Mannheim Study of Children at Risk were evaluated for pleasurable and unpleasant experiences during their initial smoking experience. A significant sex-by-genotype effect was observed for nicotine self-administration. Male 118GG mice demonstrated higher nicotine intake than male 118AA mice, suggesting increased nicotine reinforcement. In contrast, there was no genotype effect in female mice. Human male G allele carriers reported increased pleasurable effects from their first smoking experience, as compared to male homozygous A, female G and female homozygous A allele carriers. The 118G allele appears to confer greater sensitivity to nicotine reinforcement in males, but not females.
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Affiliation(s)
- R E Bernardi
- Institute of Psychopharmacology, Central
Institute of Mental Health, Medical Faculty Mannheim/Heidelberg
University, Mannheim, Germany
| | - K Zohsel
- Department of Child and Adolescent
Psychiatry, Central Institute of Mental Health, Medical Faculty
Mannheim/Heidelberg University, Mannheim,
Germany
| | - N Hirth
- Institute of Psychopharmacology, Central
Institute of Mental Health, Medical Faculty Mannheim/Heidelberg
University, Mannheim, Germany
| | - J Treutlein
- Genetic Epidemiology, Central Institute
of Mental Health, Medical Faculty Mannheim/Heidelberg University,
Mannheim, Germany
| | - M Heilig
- Center for Social and Affective
Neuroscience, Linköping University, Linköping,
Sweden
| | - M Laucht
- Department of Child and Adolescent
Psychiatry, Central Institute of Mental Health, Medical Faculty
Mannheim/Heidelberg University, Mannheim,
Germany
| | - R Spanagel
- Institute of Psychopharmacology, Central
Institute of Mental Health, Medical Faculty Mannheim/Heidelberg
University, Mannheim, Germany
| | - W H Sommer
- Institute of Psychopharmacology, Central
Institute of Mental Health, Medical Faculty Mannheim/Heidelberg
University, Mannheim, Germany,Addiction Medicine, Central Institute of
Mental Health, Medical Faculty Mannheim/Heidelberg University,
Mannheim, Germany,Institute of Psychopharmacology, Central Institute of Mental
Health, Medical Faculty Mannheim/Heidelberg University, Square
J5, Mannheim
68159, Germany; E-mail:
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16
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Bernardi RE, Broccoli L, Spanagel R, Hansson AC. Sex differences in dopamine binding and modafinil conditioned place preference in mice. Drug Alcohol Depend 2015; 155:37-44. [PMID: 26342627 DOI: 10.1016/j.drugalcdep.2015.08.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 08/21/2015] [Accepted: 08/21/2015] [Indexed: 01/06/2023]
Abstract
BACKGROUND Studies in humans and rodents have demonstrated under certain conditions some reinforcing properties of modafinil, a drug being examined clinically for its potential to treat psychostimulant abuse. However, the majority of rodent studies examining the abuse potential of modafinil have used high doses that may not be clinically relevant. In fact, recent work has indicated that doses similar to those administered to humans are not reinforcing in mice. METHODS The current study examined sex differences in the ability of low-dose modafinil (0.75mg/kg, IP) to induce a conditioned place preference in mice, and assessed sex-dependent alterations in dopamine D1, D2 and DAT binding sites in reward-related regions in naïve and modafinil-treated mice. RESULTS Low-dose modafinil failed to induce a conditioned place preference in male mice, while female mice demonstrated a significant modafinil place preference. Several dopamine binding differences were also detected in naïve and modafinil-treated mice, including sex differences in D1 and D2 availability in reward-related regions, and are discussed in relation to sex-dependent differences in the reinforcing effects of modafinil and psychostimulants in general. CONCLUSIONS These findings implicate sex differences in the reinforcing properties of modafinil in mice, and indicate that clinical evaluation of the sex dependence of the reinforcing properties of modafinil in humans is warranted.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5, 68159, Mannheim, Germany.
| | - Laura Broccoli
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5, 68159, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5, 68159, Mannheim, Germany
| | - Anita C Hansson
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5, 68159, Mannheim, Germany
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17
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Abstract
The aim of Addiction Biology is to advance our understanding of the action of drugs of abuse and addictive processes via the publication of high-impact clinical and pre-clinical findings resulting from behavioral, molecular, genetic, biochemical, neurobiological and pharmacological research. As of 2013, Addiction Biology is ranked number 1 in the category of Substance Abuse journals (SCI). Occasionally, Addiction Biology likes to highlight via review important findings focused on a particular topic and recently published in the journal. The current review summarizes a number of key publications from Addiction Biology that have contributed to the current knowledge of nicotine research, comprising a wide spectrum of approaches, both clinical and pre-clinical, at the cellular, molecular, systems and behavioral levels. A number of findings from human studies have identified, using imaging techniques, alterations in common brain circuits, as well as morphological and network activity changes, associated with tobacco use. Furthermore, both clinical and pre-clinical studies have characterized a number of mechanistic targets critical to understanding the effects of nicotine and tobacco addiction. Together, these findings will undoubtedly drive future studies examining the dramatic impact of tobacco use and the development of treatments to counter nicotine dependence.
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Affiliation(s)
- Rick E. Bernardi
- Institute of Psychopharmacology; Central Institute of Mental Health; Medical Faculty Mannheim/Heidelberg University; Germany
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18
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Zlatković J, Todorović N, Tomanović N, Bošković M, Djordjević S, Lazarević-Pašti T, Bernardi RE, Djurdjević A, Filipović D. Chronic administration of fluoxetine or clozapine induces oxidative stress in rat liver: a histopathological study. Eur J Pharm Sci 2014; 59:20-30. [PMID: 24768740 DOI: 10.1016/j.ejps.2014.04.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 02/28/2014] [Accepted: 04/13/2014] [Indexed: 12/16/2022]
Abstract
Chronic exposure to stress contributes to the etiology of mood disorders, and the liver as a target organ of antidepressant and antipsychotic drug metabolism is vulnerable to drug-induced toxicity. We investigated the effects of chronic administration of fluoxetine (15mg/kg/day) or clozapine (20mg/kg/day) on liver injury via the measurement of liver enzymes, oxidative stress and histopathology in rats exposed to chronic social isolation (21days), an animal model of depression, and controls. The activity of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), the liver content of carbonyl groups, malonyldialdehyde (MDA), reduced glutathione (GSH), cytosolic glutathione S-transferase (GST) and nitric oxide (NO) metabolites were determined. We also characterized nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2) and CuZn-superoxide dismutase (CuZnSOD) protein expression as well as histopathological changes. Increased serum ALT activity in chronically-isolated and control animals treated with both drugs was found while increased AST activity was observed only in fluoxetine-treated rats (chronically-isolated and controls). Increased carbonyl content, MDA, GST activity and decreased GSH levels in drug-treated controls/chronically-isolated animals suggest a link between drugs and hepatic oxidative stress. Increased NO levels associated with NF-κB activation and the concomitant increased COX-2 expression together with compromised CuZnSOD expression in clozapine-treated chronically-isolated rats likely reinforce oxidative stress, observed by increased lipid peroxidation and GSH depletion. In contrast, fluoxetine reduced NO levels in chronically-isolated rats. Isolation induced oxidative stress but histological changes were similar to those observed in vehicle-treated controls. Chronic administration of fluoxetine in both chronically-isolated and control animals resulted in more or less normal hepatic architecture, while clozapine in both groups resulted in liver injury. These data suggest that clozapine appears to have a higher potential to induce liver toxicity than fluoxetine.
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Affiliation(s)
- Jelena Zlatković
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, Serbia
| | - Nevena Todorović
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, Serbia
| | - Nada Tomanović
- Institute of Pathology, School of Medicine, University of Belgrade, Serbia
| | - Maja Bošković
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, Serbia
| | | | - Tamara Lazarević-Pašti
- Department of Physical Chemistry, Institute of Nuclear Sciences "Vinča", University of Belgrade, Serbia
| | - Rick E Bernardi
- Central Institute of Mental Health, Institute of Psychopharmacology, Mannheim, Germany
| | | | - Dragana Filipović
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, Serbia.
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19
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Bernardi RE, Spanagel R. Basal activity level in mice predicts the initial and sensitized locomotor response to nicotine only in high responders. Behav Brain Res 2014; 264:143-50. [PMID: 24508239 DOI: 10.1016/j.bbr.2014.01.046] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 01/28/2014] [Indexed: 02/05/2023]
Abstract
Not all humans become addicted to drugs of abuse following casual use. Thus, it is important to identify factors that may contribute to subsequent drug responding. Previous studies have identified characteristics such as novelty-seeking, impulsivity, and anxiety as factors involved in the progression to drug dependence. The current experiment investigated basal locomotor activity in C57Bl/6N mice as a potential predictor of subsequent nicotine responses. We examined the ability of differences in basal locomotor activity to predict the acute and sensitized response to nicotine, as well as nicotine conditioned reinforcement. A median split was used to distinguish between low and high responders with regard to basal locomotor activity in mice. We then measured the acute response to nicotine (0.5mg/kg IP) in these mice, followed by measures of conditioned place preference (CPP; 0.5mg/kg IP) and locomotor sensitization (0.5mg/kg IP), to determine whether basal locomotion is predictive of subsequent responding to nicotine. High, but not low, basal activity was found to be a predictor of both the acute and sensitized response to nicotine. Interestingly, only mice classified as having low basal activity demonstrated a significant CPP, suggesting that pre-exposure to nicotine differentially affects conditioned reinforcement on the basis of initial activity level. Basal locomotor activity may be an efficient measure of subsequent locomotor responding to nicotine, but only in animals classified as having high basal activity. However, animals with low basal locomotor activity may be more susceptible to the reinforcing properties of nicotine.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5 68159 Mannheim, Germany.
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim/Heidelberg University, J5 68159 Mannheim, Germany
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20
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Bernardi RE, Uhrig S, Spanagel R, Hansson AC. Transcriptional regulation of L-type calcium channel subtypes Cav1.2 and Cav1.3 by nicotine and their potential role in nicotine sensitization. Nicotine Tob Res 2014; 16:774-85. [PMID: 24470632 DOI: 10.1093/ntr/ntt274] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
INTRODUCTION L-type calcium channel (LTCC) activity in the brain is mediated by 2 subtypes, Ca(v)1.2 and Ca(v)1.3. The individual contributions of these LTCC subtypes to the long-term pharmacological and behavioral effects of nicotine are unknown. METHODS Using quantitative in situ hybridization, we examined expression levels of Ca(v)1.2 and Ca(v)1.3 in forebrain regions of mice treated with nicotine (0.175 mg/kg) or saline for 1 or 14 days and sacrificed 24 hr or 7 days following the last injection. Additionally, we treated mice with nicotine for 14 days and then administered the nonspecific LTCC antagonist nifedipine twice daily during a 7-day abstinence period prior to testing for nicotine sensitization to determine the effect of LTCC blockade on sensitization. RESULTS Ca(v)1.2 mRNA was unaffected 24 hr following a single nicotine exposure, whereas Ca(v)1.3 mRNA was upregulated in several brain regions. Following 14 days of nicotine treatment and 24 hr of abstinence, Ca(v)1.2 mRNA was downregulated throughout the areas examined, whereas Ca(v)1.3 mRNA had mostly returned to control values. Following 7 days of abstinence, a strong upregulation of Ca(v)1.2 transcripts was observed, whereas Ca(v)1.3 mRNA was largely unaffected. In our sensitization study, nifedipine administered during nicotine abstinence impaired subsequent nicotine sensitization. CONCLUSIONS Our data suggest a differential involvement of Ca(v)1.2 and Ca(v)1.3 in nicotine-related processes. Ca(v)1.3 seems to be involved primarily during early exposure to nicotine. Ca(v)1.2 appears to play a role in the long-term molecular and behavioral changes that occur following chronic nicotine and abstinence. Nifedipine may counteract those nicotine-induced alterations in LTCC activity to impair nicotine sensitization.
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Affiliation(s)
- Rick E Bernardi
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim /University of Heidelberg, Mannheim, Germany
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22
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Zlatković J, Bernardi RE, Filipović D. Protective effect of Hsp70i against chronic social isolation stress in the rat hippocampus. J Neural Transm (Vienna) 2013; 121:3-14. [PMID: 23851625 DOI: 10.1007/s00702-013-1066-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/02/2013] [Indexed: 12/29/2022]
Abstract
Stress-related glucocorticoids and glutamate release has been implicated in depression. Glutamate neurotoxicity is mediated, in part, by the production of nitric oxide via nitric oxide synthase (NOS) isoforms and mitochondrial damage. We previously reported that chronic social isolation stress triggers proapoptotic signaling in the rat prefrontal cortex, but not in the hippocampus. Given that the hippocampus is highly sensitive to stress, we examined signaling cascades underlying the hippocampal cellular protection through the NOS pathway, antioxidant capacity and heat shock protein (Hsp) expression. We investigated neuronal (nNOS) and inducible (iNOS) protein levels, subcellular protein distributions of nuclear factor-κB (NF-κB), CuZnSOD and MnSOD activity, reduced glutathione (GSH), stress-inducible Hsp70 (Hsp70i) protein expression and serum corticosterone (CORT) levels of rats exposed to 21 days of chronic social isolation, an animal model of depression, alone or in combination with 2 h of acute immobilization or cold stress (combined stress). Both acute stressors elevated CORT, with lesser magnitude increase in chronically isolated rats exposed to novel acute stress as compared to acute stressors alone, indicating compromised HPA axis activity. Acute cold decreased nuclear CuZnSOD activity and stimulated NF-κB nuclear translocation. Chronic social isolation resulted in no activation of NF-κB, but led to decreased GSH, iNOS and increased nNOS and Hsp70i levels, alterations that remained following combined stressors. Decreased mitochondrial MnSOD activity after combined stressors suggests compromised detoxifying capacity. These data indicate that Hsp70i upregulation may provide hippocampal cellular protection against chronic social isolation stress mediated by downregulation of iNOS protein expression through suppression of NF-κB activation.
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Affiliation(s)
- Jelena Zlatković
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences "Vinča", University of Belgrade, P. O. Box 522-090, 11001, Belgrade, Serbia
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23
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Bernardi RE, Lattal KM. Post-conditioning propranolol disrupts cocaine sensitization. Pharmacol Biochem Behav 2012; 102:515-9. [PMID: 22750295 DOI: 10.1016/j.pbb.2012.06.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 06/11/2012] [Accepted: 06/19/2012] [Indexed: 11/12/2022]
Abstract
Antagonists of β-adrenergic receptors (β-ARs) have previously been demonstrated to impair long-term memory in a variety of animal behavioral paradigms. Surprisingly little is known about the ability of β-ARs to modulate initial memory formation in drug conditioning paradigms. The current study examined whether the post-training administration of the β-AR antagonist, propranolol, would disrupt single-trial cocaine-induced sensitization. Rats received 10 mg/kg propranolol immediately following a 30-min cocaine or vehicle exposure in a conditioning context and were later tested for their locomotor response to a cocaine challenge. Rats that received propranolol following cocaine conditioning showed an impairment of locomotor sensitization during testing. However, this effect was only seen in animals with an initial sensitivity to the locomotor effects of cocaine. Rats that failed to show a locomotor response to cocaine during conditioning were not affected by propranolol. We discuss the implications of these findings as they relate to drug conditioning and memory consolidation studies.
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Affiliation(s)
- Rick E Bernardi
- Oregon Health & Science University, Department of Behavioral Neuroscience, L470, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, United States.
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24
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Bernardi RE, Lattal KM. A role for alpha-adrenergic receptors in extinction of conditioned fear and cocaine conditioned place preference. Behav Neurosci 2010; 124:204-10. [PMID: 20364880 DOI: 10.1037/a0018909] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Previous work has demonstrated an important role for adrenergic receptors in memory processes in fear and drug conditioning paradigms. Recent studies have also demonstrated alterations in extinction in these paradigms using drug treatments targeting beta- and alpha2-adrenergic receptors, but little is known about the role of alpha-adrenergic receptors in extinction. The current study examined whether antagonism of alpha-adrenergic receptors would impair the consolidation of extinction in fear and cocaine conditioned place preference paradigms. After contextual fear conditioning, injections of the alpha-adrenergic receptor antagonist prazosin (1.0 or 3.0 mg/kg) following nonreinforced context exposures slowed the loss of conditioned freezing over the course of 5 extinction sessions (Experiment 1). After cocaine place conditioning, prazosin had no effect on the rate of extinction over 8 nonreinforced test sessions. Following postextinction reconditioning, however, prazosin-treated mice showed a robust place preference, but vehicle-treated mice did not, suggesting that prazosin reduced the persistent effects of extinction (Experiment 2). These results confirm the involvement of the alpha-adrenergic receptor in extinction processes in both appetitive and aversive preparations.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA
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Bernardi RE, Ryabinin AE, Berger SP, Lattal KM. Post-retrieval disruption of a cocaine conditioned place preference by systemic and intrabasolateral amygdala beta2- and alpha1-adrenergic antagonists. Learn Mem 2009; 16:777-89. [PMID: 19940038 DOI: 10.1101/lm.1648509] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Previous work has demonstrated post-retrieval impairment in associative learning paradigms, including those mediated by drugs of abuse, using nonspecific beta-adrenergic receptor (beta-AR) antagonists. Remarkably little is known about the role of the specific beta-AR subtypes, or other adrenergic receptors, in these effects. The current study examined the effects of beta(1) and beta(2), as well as alpha(1)-adrenergic receptor antagonism following retrieval of a cocaine conditioned place preference (CPP). We found that rats administered the beta(2) antagonist ICI 118,551 (8 mg/kg intraperitoneal [IP]) or the alpha(1) antagonist prazosin (1 mg/kg IP) following a drug-free test for CPP showed attenuated preference during a subsequent test, while the beta(1) antagonist betaxolol (5 or 10 mg/kg IP) and a lower dose of prazosin (0.3 mg/kg IP) had no effect. Furthermore, post-test microinfusion of ICI 118,551 (6 nmol/side) or prazosin (0.5 nmol/side) into the basolateral amygdala (BLA) also impaired a subsequent preference. Systemic or intra-BLA ICI 118,551 or prazosin administered to rats in their home cages, in the absence of a preference test, had no effect on CPP 24 h later. ICI 118,551 also attenuated the FOS response in the BLA induced by the CPP test. These results are the first to demonstrate a role for alpha(1)- and beta(2)-specific adrenergic mechanisms in post-retrieval memory processes. These systemic and site-specific injections, as well as the FOS immunohistochemical analyses, implicate the importance of specific noradrenergic signaling mechanisms within the BLA in post-retrieval plasticity.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oregon 97239, USA.
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Bernardi RE, Lewis JR, Lattal KM, Berger SP. Modafinil reinstates a cocaine conditioned place preference following extinction in rats. Behav Brain Res 2009; 204:250-3. [PMID: 19482046 DOI: 10.1016/j.bbr.2009.05.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 05/21/2009] [Accepted: 05/23/2009] [Indexed: 11/17/2022]
Abstract
The current study examined whether modafinil would reinstate an extinguished cocaine conditioned place preference (CPP). Following extinction of a cocaine CPP, rats were administered modafinil (128 mg/kg), cocaine (5 mg/kg) or vehicle and given a 60-min reinstatement test. While the effect of cocaine was transient, modafinil robustly reinstated a cocaine CPP following extinction, suggesting that modafinil may induce relapse or increase the vulnerability of addicts to the reinforcing effects of environmental triggers.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA.
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Abstract
The idea that learning proceeds as a function of the discrepancy (or error) between expected and obtained outcomes is central to many theories of associative learning. However, remarkably little is known about the neurobiological mechanisms that underlie this learning of predictive errors in fear conditioning, a widely used preparation in studies of cellular and molecular mechanisms of memory. In this issue of Behavioral Neuroscience, S. Cole and G. P. McNally demonstrate an important dissociation between the establishment and regulation of predictive error at the cellular level. Their findings have added a level of complexity to currently established views of the function of NMDA and opioid receptors in learning and memory. This commentary discusses some of the implications of these findings for theoretical and neurobiological approaches to memory, as well as current thinking about the cellular circuitry involved in reward learning and drug abuse.
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Affiliation(s)
- K Matthew Lattal
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, USA.
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Ettenberg A, Bernardi RE. Effects of buspirone on the immediate positive and delayed negative properties of intravenous cocaine as measured in the conditioned place preference test. Pharmacol Biochem Behav 2007; 87:171-8. [PMID: 17524462 PMCID: PMC1949322 DOI: 10.1016/j.pbb.2007.04.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 04/16/2007] [Accepted: 04/19/2007] [Indexed: 11/29/2022]
Abstract
In prior work, we have demonstrated that the behavioral effects of cocaine adhere to the predictions of the opponent-process theory of drug action. Animals develop conditioned place preferences for distinct locations paired with the immediate effects of IV cocaine, but learn to avoid places paired with the effects present 15-min post-injection. It was of interest to assess the putative role of 5-HT in producing the negative properties of cocaine since cocaine acts to inhibit the reuptake of serotonin (5-HT) and since such actions have been associated with anxiogenic consequences. Male rats were administered a reinforcing dose of cocaine (1.0 mg/kg IV) and then placed - either immediately or after a 15-min delay - into one side of a two-compartment (black-white) conditioned place preference (CPP) box for 5-min. On alternate days, the animals received IV saline injections and were placed in the opposite side of the CPP box. This continued for eight days after which animals had experienced 4 pairings of cocaine with one side (black or white) of the CPP apparatus, and 4 saline pairings with the opposite side. Other groups of rats were treated identically except that 30-min prior to placement into the apparatus, these animals received an IP injection of saline or buspirone (a partial 5-HT1A agonist) at a dose that we have shown to be anxiolytic (2.5 mg/kg IP). Control animals experienced either buspirone or saline pretreatments without cocaine. Our results confirm that animals increase the time spent on the side paired with the immediate effects of cocaine (compared to baseline), but tend to avoid the side paired with effects present 15-min post-injection. Buspirone had no effect on the immediate rewarding properties of cocaine, but completely reversed the negative properties present 15-min post-cocaine. These results are consistent with the view that attenuation of 5-HT neurotransmission (via the autoreceptor agonist properties of buspirone) can reverse the negative impact of IV cocaine.
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Affiliation(s)
- Aaron Ettenberg
- Behavioral Pharmacology Laboratory, Department of Psychology, University of California, Santa Barbara, CA 93106-9660, USA.
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Abstract
In experiments examining the potential reconsolidation of drug-associated contextual memories, rats were given a single pairing of cocaine with a specific context, and the ability of the protein synthesis inhibitor anisomycin administered following a context-only memory retrieval trial to impair conditioned locomotor sensitization was tested. Rats receiving 150 mg/kg anisomycin immediately following a 5-min reexposure to the cocaine-conditioned context showed decreased activity compared with the vehicle control group in response to a low-dose cocaine challenge during a subsequent test for conditioned sensitization. This effect was not seen when anisomycin was administered following a 30-min reexposure to the context or when anisomycin was administered 25 min after a 5-min reexposure. These results are consistent with a growing literature suggesting that following retrieval, associative contextual memories may undergo a transient protein synthesis-dependent reconsolidation phase that normally serves to maintain memory.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA.
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Abstract
The current study examined whether a postretrieval drug memory could be disrupted by the beta-adrenoceptor antagonist propranolol, administered following reactivation in a cocaine-mediated conditioned place preference paradigm. Following cocaine conditioning, rats were given a test of conditioned place preference, followed immediately by intraperitoneal administration of propranolol or saline. Rats that received propranolol following the preference test showed no preference for the cocaine-paired floor during a subsequent test, while vehicle-treated rats continued to express a preference for the cocaine-paired floor. These deficits in behavior were specific to retrieval of the cocaine-mediated memory, suggesting that postretrieval propranolol induced an impairment of drug-seeking behavior that is consistent with the disruption of a reconsolidation phase following retrieval.
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Affiliation(s)
- Rick E Bernardi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland Veterans Affairs Medical Center, Portland, Oregon 97239, USA.
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Ettenberg A, Bernardi RE. Anxiolytic-like actions of buspirone in a runway model of intravenous cocaine self-administration. Pharmacol Biochem Behav 2006; 85:393-9. [PMID: 17064759 PMCID: PMC1851937 DOI: 10.1016/j.pbb.2006.09.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2006] [Revised: 09/02/2006] [Accepted: 09/11/2006] [Indexed: 10/24/2022]
Abstract
In previous work from our laboratory, rats traversing a straight alley for a reward of IV cocaine have been observed to develop ambivalence about entering the goal box. Over trials, animals repeatedly run toward the goal box, stop at the entry point, and then retreat back toward the start box. This unique pattern of retreat behavior has been shown to reflect a form of "approach-avoidance conflict" that stems from the subjects' concurrent positive (cocaine reward) and negative (cocaine-induced anxiety) associations with the goal box. Buspirone, a partial 5-HT(1A) agonist, has been reported to produce anxiolytic-like actions in the clinic, but has had mixed results in experimental tests of anxiety using animal subjects. Since most animal tests of conflict/anxiety employ the administration of foot-shock - a relatively strong aversive stimulus - it was of interest to determine whether buspirone would alter the more subtle approach-avoidance conflict observed in well-trained animals running a straight alley for single daily injections of 1.0 mg/kg IV cocaine. Runway testing consisted of single daily trials that continued until consistent approach-avoidance retreats were exhibited. Each animal was then pretreated 30 min prior to runway testing with vehicle and one of three doses of buspirone (0.0, 1.0, 2.5 or 5.0 mg/kg IP). Testing continued in a counterbalanced manner until all rats had experienced each dose of buspirone with 3 days of cocaine-only trials between each test day. The number of retreats exhibited on each trial served as an index of the approach-avoidance conflict present on that trial. Results clearly demonstrated that buspirone (at the two higher doses) attenuated the retreat behavior of animals approaching a goal box for IV cocaine -- an action consistent with its anxiolytic-like actions in the clinic.
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Affiliation(s)
- Aaron Ettenberg
- Behavioral Pharmacology Laboratory, Department of Psychology, University of California, Santa Barbara, CA 93106-9660, USA.
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Abstract
The present study describes an objective, cost- and time-efficient procedure for characterizing the ataxic effects of psychoactive drugs. Male Sprague-Dawley rats were administered an intraperitoneal injection of either saline or one of three doses (1, 5 or 10 mg/kg) of phencyclidine (PCP) 15 min prior to being placed into an empty standard operant conditioning chamber (all manipulanda were removed). The floor of the test apparatus consisted of parallel rows of metal rods spaced approximately 1.5 cm apart. During a 5-min test, a single observer counted the frequency with which each animal's paws (front or back) slipped between the rows of bars that constituted the cage floor. The data demonstrated that while saline animals exhibited no instability in their ambulation, PCP-treated animals demonstrated a highly reliable dose-dependent increase in the number of "paw slips" in a single trial. Since animals are known to develop tolerance to the ataxic response to PCP, the validity of the test as a measure of drug-induced ataxia was examined in a separate group of animals treated with the middle (5 mg/kg) dose every other day over the course of a 9-day period (i.e., resulting in five injection trials). In this experiment, each subsequent test produced a reliable reduction in the magnitude of the ataxic response, and by the fifth drug challenge, the PCP animals were performing at near-control levels. These results suggest that the "paw slip test" can serve as a simple, reliable, objective and valid measure of drug-induced ataxia. The relevance of the ataxia data for interpreting the locomotor response of animals treated with PCP is also discussed.
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Affiliation(s)
- Susan M Melnick
- Behavioral Pharmacology Laboratory, Department of Psychology, University of California-Santa Barbara, Santa Barbara, CA 93106-9660, USA
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