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Impaired discriminative avoidance and increased plasma corticosterone levels induced by vaginal lavage procedure in rats. Physiol Behav 2021; 232:113343. [DOI: 10.1016/j.physbeh.2021.113343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/26/2021] [Accepted: 01/28/2021] [Indexed: 12/26/2022]
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2
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Effects of plus-maze experience and chlordiazepoxide on anxiety-like behavior and serotonin neural activity in the dorsal raphe nucleus in rats. Behav Pharmacol 2020; 30:208-219. [PMID: 30169377 DOI: 10.1097/fbp.0000000000000423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The extent to which rats express anxiety-like behavior on the elevated plus-maze (EPM) depends on their previous maze experience. Open-arm avoidance develops in maze-experienced rats, and is often accompanied by a diminished anxiolytic response to benzodiazepines. Regions of the dorsal raphe nucleus (DRN) were examined in male Sprague-Dawley rats using c-Fos and serotonin immunohistochemistry following a single exposure, a second exposure or no exposure to the EPM. We then examined the effect of the benzodiazepine anxiolytic chlordiazepoxide (CDP, 5 mg/kg) on EPM behavior and DRN neural activity. Enhanced open-arm avoidance was evident on the second EPM trial in both experiments. The observed pattern of c-Fos expression suggests that the first exposure to the maze activates serotonin cells in the rostral and dorsal regions of the DRN and that only the dorsal subregion is activated by a second exposure. CDP increased open-arm exploration during the first trial, which corresponded to decreased 5-hydroxytryptamine (5-HT) activity in the rostral and ventral subregions of the DRN. However, 5-HT activity in the DRN was reduced in rats on the second maze trial compared with the first trial, when CDP had no effect on open-arm exploration. These results suggest that open-arm avoidance in maze-experienced rats can be characterized as a coping response that is mediated by specific populations of 5-HT neurons in the DRN.
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3
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Bernabucci M, Zhuo M. Calcium activated adenylyl cyclase AC8 but not AC1 is required for prolonged behavioral anxiety. Mol Brain 2016; 9:60. [PMID: 27234425 PMCID: PMC4884383 DOI: 10.1186/s13041-016-0239-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 05/12/2016] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Anxiety disorder is a state of mental discomfort while acute anxiety induces an enhancement of vigilance/arousal or increased anxious responses. Most of the previous studies investigated basic mechanisms for acute anxiety, while less information is available for prolonged or repetitive anxiety. RESULTS In the present study, we wanted to examine possible molecular mechanisms for behavioral anxiety after repeated exposures. Performing a paradigm of five sessions of the elevated plus-maze (EPM), we show that the repeated exposure to the EPM induces a long-lasting anxiety causing a gradual increase of anxiolytic activity, which is maintained for at least 21 days. Genetic deletion of AC8 (adenylyl cyclase 8) but not AC1 abolished long-lasting anxiety. CONCLUSIONS Our results suggest that calcium-stimulated AC8 is required to sustain the long-lasting anxiety caused by repeated EPM testing, and we can identify in AC8 a novel target for treating anxiety-related mood disorders.
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Affiliation(s)
- Matteo Bernabucci
- Department of Physiology, Faculty of Medicine, University of Toronto, University of Toronto Center for the study of pain, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Min Zhuo
- Department of Physiology, Faculty of Medicine, University of Toronto, University of Toronto Center for the study of pain, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada.
- Center for Neuron and Disease, Frontier Institutes of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.
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Bomfim GHS, Verde LF, Frussa-Filho R, Jurkiewicz A, Jurkiewicz NH. Functional effects of alcohol withdrawal syndrome on peripheral sympathetic neurotransmission in vas deferens of adult rats. Life Sci 2014; 108:34-43. [PMID: 24831557 DOI: 10.1016/j.lfs.2014.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 04/14/2014] [Accepted: 05/02/2014] [Indexed: 01/19/2023]
Abstract
AIMS Alcohol withdrawal syndrome (AWS) is characterized by a set of physiological modifications triggered by abrupt withdrawal and/or decreasing consumption of ethanol (EtOH), which may manifest 16-48 h after ceasing consumption. The relationship between the effects of AWS and central and peripheral sympathetic neurotransmission is unknown. This study investigates the possible mechanisms on the sympathetic system during periods of AWS. MAIN METHODS Male Wistar rats were treated with EtOH (6-10 g/kg/day/v.o. 5 days). Subsequently, 1h, 24h, 48 h and 120 h after administration of the last dose of EtOH, the animals were sacrificed, and their vas deferens (VD) were removed to perform the following evaluations: (a) concentration-effect curves of sympathetic agonist; (b) activity of α2-adrenoreceptor; (c) function of voltage-dependent calcium channels (Cav); and (d) release of endogenous catecholamines measured in real time coupled to HPLC. KEY FINDINGS The results showed that the maximum effects of contraction were increased by agonists tested in at 24h and 48 h EtOH withdrawal. The inhibitory affinity (pIC50) of guanfacine was decreased 24h EtOH withdrawal. The function of Cav was also decreased as pIC50 values dropped 24h and 48 h EtOH withdrawal. The release of catecholamines increased 48 h after EtOH withdrawal. It is suggested that AWS triggers hyperactivity in peripheral sympathetic neurotransmission. SIGNIFICANCE The mechanisms underlying hyperactivity are possibly explained by a failure of autoregulation from catecholamines released by α2-adrenoreceptors and/or an increase of Cav function, which may be potential targets to attenuate the symptoms of AWS at the peripheral level.
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Affiliation(s)
| | - Luciana Ferreira Verde
- Department of Pharmacology, Federal University of São Paulo (Unifesp), Rua 3 de maio 100, 04044-020 São Paulo, SP, Brazil
| | - Roberto Frussa-Filho
- Department of Pharmacology, Federal University of São Paulo (Unifesp), Rua 3 de maio 100, 04044-020 São Paulo, SP, Brazil
| | - Aron Jurkiewicz
- Department of Pharmacology, Federal University of São Paulo (Unifesp), Rua 3 de maio 100, 04044-020 São Paulo, SP, Brazil.
| | - Neide Hyppolito Jurkiewicz
- Department of Pharmacology, Federal University of São Paulo (Unifesp), Rua 3 de maio 100, 04044-020 São Paulo, SP, Brazil
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5
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Novelty and anxiolytic drugs dissociate two components of hippocampal theta in behaving rats. J Neurosci 2013; 33:8650-67. [PMID: 23678110 DOI: 10.1523/jneurosci.5040-12.2013] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hippocampal processing is strongly implicated in both spatial cognition and anxiety and is temporally organized by the theta rhythm. However, there has been little attempt to understand how each type of processing relates to the other in behaving animals, despite their common substrate. In freely moving rats, there is a broadly linear relationship between hippocampal theta frequency and running speed over the normal range of speeds used during foraging. A recent model predicts that spatial-translation-related and arousal/anxiety-related mechanisms of hippocampal theta generation underlie dissociable aspects of the theta frequency-running speed relationship (the slope and intercept, respectively). Here we provide the first confirmatory evidence: environmental novelty decreases slope, whereas anxiolytic drugs reduce intercept. Variation in slope predicted changes in spatial representation by CA1 place cells and novelty-responsive behavior. Variation in intercept predicted anxiety-like behavior. Our findings isolate and doubly dissociate two components of theta generation that operate in parallel in behaving animals and link them to anxiolytic drug action, novelty, and the metric for self-motion.
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Valente MF, Romariz S, Calcagnotto ME, Ruiz L, Mello LE, Frussa-Filho R, Longo BM. Postnatal Transplantation of Interneuronal Precursor Cells Decreases Anxiety-Like Behavior in Adult Mice. Cell Transplant 2013; 22:1237-47. [DOI: 10.3727/096368912x657422] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The GABAergic system is critically involved in the modulation of anxiety levels, and dysfunction of GABAergic neurotransmission appears to be involved in the development of generalized anxiety disorder. Precursor cells from the medial ganglionic eminence (MGE) have the ability to migrate and differentiate into inhibitory GABAergic interneurons after being transplanted into the mouse brain. Thus, transplantation of interneuronal precursor cells derived from the MGE into a postnatal brain could modify the neuronal circuitry, increasing GABAergic tone and decreasing anxiety-like behavior in animals. Our aim was to verify the in vivo effects of transplanted MGE cells by evaluating anxiety-like behavior in mice. MGE cells from 14-day green fluorescent protein (GFP) embryos were transplanted into newborn mice. At 15, 30, and 60 days posttransplant, the animals were tested for anxiety behavior with the elevated plus maze (EPM) test. Our results show that transplanted cells from MGE were able to migrate to different regions of the brain parenchyma and to differentiate into inhibitory interneurons. The neuronal precursor cell transplanted animals had decreased levels of anxiety, indicating a specific function of these cells in vivo. We suggested that transplantation of MGE-derived neuronal precursors into neonate brain could strengthen the inhibitory function of the GABAergic neuronal circuitry related to anxiety-like behavior in mice.
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Affiliation(s)
- M. F. Valente
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - S. Romariz
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - M. E. Calcagnotto
- Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - L. Ruiz
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - L. E. Mello
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - R. Frussa-Filho
- Department of Pharmacology, Universidade Federal de São Paulo, São Paulo, Brazil
| | - B. M. Longo
- Department of Physiology, Universidade Federal de São Paulo, São Paulo, Brazil
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Horváth J, Szögi T, Müller G, Szegedi V. The anxiolytic buspirone shifts coping strategy in novel environmental context of mice with different anxious phenotype. Behav Brain Res 2013; 250:32-8. [PMID: 23608485 DOI: 10.1016/j.bbr.2013.04.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 04/10/2013] [Accepted: 04/13/2013] [Indexed: 10/26/2022]
Abstract
Patients suffering from anxiety disorders show increased fear when encounter a novel environment. Rodents, placed in new environmental context may respond either with increased novelty seeking (active), or enhanced anxiety (passive coping style), which may depend on the trait anxiety of the animal. Here, the connection between the initial level of anxiety and the behavioral responses in a novel environment was investigated. Two inbred mouse strains having either high- or low-anxiety related behavior (AX and nAX) were exposed to elevated plus maze (EPM), a standard test for assessing anxiety level, for 8 consecutive days. The initial anxiety level was modulated by chronic treatment with buspirone (bus) treatment, a clinically effective anxiolytic, using 2.5mg/kg and 5.0mg/kg doses. Both strains showed a gradual decrease of open-arm exploration, which was not prevented by bus treatment. Another cohort of animals was exposed to EPM for 2 days, and then we changed to blue light illumination and used a different cleaning substance with citrus odor (context change, CC). It was found that upon CC AX mice exhibited increased, while nAX mice showed decreased anxiety. Bus in 2.5mg/kg changed the coping strategy from passive to active exploration after CC in the AX mice; however, the same treatment rendered nAX mice passive upon CC. Bus in 5.0mg/kg failed to alter the overall coping style in the novel environment of both strains. These results suggest that these mouse lines use different coping strategy in novel context, which can be changed with bus treatment.
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Affiliation(s)
- János Horváth
- Department of Medical Chemistry, University of Szeged, Szeged, Hungary
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Zanin KA, Patti CL, Sanday L, Fernandes-Santos L, Oliveira LC, Poyares D, Tufik S, Frussa-Filho R. Effects of zolpidem on sedation, anxiety, and memory in the plus-maze discriminative avoidance task. Psychopharmacology (Berl) 2013; 226:459-74. [PMID: 22729271 DOI: 10.1007/s00213-012-2756-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 05/21/2012] [Indexed: 01/01/2023]
Abstract
RATIONALE Zolpidem (Zolp), a hypnotic drug prescribed to treat insomnia, may have negative effects on memory, but reports are inconsistent. OBJECTIVES We examined the effects of acute doses of Zolp (2, 5, or 10 mg/kg, i.p.) on memory formation (learning, consolidation, and retrieval) using the plus-maze discriminative avoidance task. METHODS Mice were acutely treated with Zolp 30 min before training or testing. In addition, the effects of Zolp and midazolam (Mid; a classic benzodiazepine) on consolidation at different time points were examined. The possible role of state dependency was investigated using combined pre-training and pre-test treatments. RESULTS Zolp produced a dose-dependent sedative effect, without modifying anxiety-like behavior. The pre-training administration of 5 or 10 mg/kg resulted in retention deficits. When administered immediately after training or before testing, memory was preserved. Zolp post-training administration (2 or 3 h) impaired subsequent memory. There was no participation of state dependency phenomenon in the amnestic effects of Zolp. Similar to Zolp, Mid impaired memory consolidation when administered 1 h after training. CONCLUSIONS Amnestic effects occurred when Zolp was administered either before or 2-3 h after training. These memory deficits are not related to state dependency. Moreover, Zolp did not impair memory retrieval. Notably, the memory-impairing effects of Zolp are similar to those of Mid, with the exception of the time point at which the drug can modify consolidation. Finally, the memory effects were unrelated to sedation or anxiolysis.
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Affiliation(s)
- Karina A Zanin
- Departamento de Psicobiologia, Universidade Federal de São Paulo, R. Napoleão de Barros, 925, 04024002 São Paulo, SP, Brazil
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Pawlak CR, Karrenbauer BD, Schneider P, Ho YJ. The Elevated Plus-Maze Test: Differential Psychopharmacology of Anxiety-Related Behavior. EMOTION REVIEW 2012. [DOI: 10.1177/1754073911421374] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The role of individual factors in behavioral neuroscience is an important, but still neglected, area of research. For example, the Elevated Plus-Maze Test has been one of the most used paradigms to gauge unconditioned aversively motivated behavior in rodents. However, despite a great number of experiments with this test there have been only few efforts to assess systematic individual variations in the elevated plus-maze and related neurobiological functions. The present review aims to give, first, a general overview and introduction about the test, and second, an animal model of anxiety based on natural variance of plus-maze behavior within a given unselected population of rats. Finally, critical aspects of such approaches in animal research are discussed, and suggestions are given as to where to go from here.
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Affiliation(s)
- Cornelius R. Pawlak
- Addictive Behavior and Addiction Medicine, Central Institute of Mental Health, Mannheim, Germany
- Chair of Biological and Clinical Psychology, School of Social Sciences, University of Mannheim, Germany
- Institute of Psychology, University of Frankfurt am Main, Germany
| | - Britta D. Karrenbauer
- Department of Experimental and Physiological Psychology, Philipps-University of Marburg, Germany
| | - Peggy Schneider
- Department of Psychopharmacology, Central Institute of Mental Health, Germany
| | - Ying-Jui Ho
- School of Psychology, Chung Shan Medical University, Taiwan, ROC
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10
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Patti CL, Zanin KA, Sanday L, Kameda SR, Fernandes-Santos L, Fernandes HA, Andersen ML, Tufik S, Frussa-Filho R. Effects of sleep deprivation on memory in mice: role of state-dependent learning. Sleep 2011; 33:1669-79. [PMID: 21120129 DOI: 10.1093/sleep/33.12.1669] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
STUDY OBJECTIVES A considerable amount of experimental evidence suggests that sleep plays a critical role in learning/memory processes. In addition to paradoxical sleep, slow wave sleep is also reported to be involved in the consolidation process of memories. Additionally, sleep deprivation can induce other behavioral modifications, such as emotionality and alternations in locomotor activity in rodents. These sleep deprivation-induced alterations in the behavioral state of animals could produce state-dependent learning and contribute, at least in part, to the amnestic effects of sleep deprivation. The aim of the present study was to examine the participation of state-dependent learning during memory impairment induced by either paradoxical sleep deprivation (PSD) or total sleep deprivation (TSD) in mice submitted to the plus-maze discriminative avoidance or to the passive avoidance task. DESIGN Paradoxical sleep deprivation (by the multiple platform method) and total sleep deprivation (by the gentle handling method) were applied to animals before training and/or testing. CONCLUSIONS Whereas pre-training or pre-test PSD impaired retrieval in both memory models, pre-training plus pre-test PSD counteracted this impairment. For TSD, pre-training, pre-test, and pre-training plus pre-test TSD impaired retrieval in both models. Our data demonstrate that PSD- (but not TSD-) memory deficits are critically related to state-dependent learning.
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Affiliation(s)
- Camilla L Patti
- Department of Pharmacology, Universidade Federal de São Paulo, São Paulo, SP, Brazil
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11
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Tolerance, sensitization and dependence to diazepam in Balb/c mice exposed to a novel open space anxiety test. Behav Brain Res 2010; 209:154-64. [PMID: 20117142 DOI: 10.1016/j.bbr.2010.01.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 01/18/2010] [Accepted: 01/24/2010] [Indexed: 02/05/2023]
Abstract
Balb/c mice were exposed to an elevated platform that is extended on two opposite sides with lowered steep slopes. They were tested for 12min per session in 6 successive days. They received i.p. administration of either saline or one dose of diazepam (DZP 0.5, 1, 3mg/kg) in sessions 1-3, and saline in sessions 4 and 5. All groups of mice received a single dose of DZP (1mg/kg) in session 6. DZP produced inverted U-shaped dose-responses on the number of entries into different areas of the apparatus, with a peak in mean response at 1mg/kg whereas its effect on the duration of entries was mostly comparable between the 3 doses. It increased the number of crossings on the surface of the platform and facilitated entries onto the slopes. DZP-treated mice crossed frequently onto and spent longer time on the slopes in sessions 1-3 whereas saline-treated mice remained on the platform in sessions 1-6. Withdrawal of DZP in sessions 4-5 increased the latency of first entry and decreased the number and duration of entries onto the slopes which was reversed with the administration of 1mg/kg of DZP in the next session. This ON-OFF the drug may be due to the half-life of DZP which is very short in mice and rats ( approximately 0.88h). It also indicates that DZP-treated mice did not benefit from previous experience of entries onto the slopes which suggests a possible "state-dependent" effect. Administration of DZP after repeated exposures to the test did not facilitate entries onto the slopes but instead increased significantly the number of crossings on the surface of the platform; this increase was much higher than that observed in mice initially treated with DZP and exposed to the test. There is no evidence of habituation in saline-treated mice: the number of crossings on the platform was comparable between the first 5 sessions of the test. These results demonstrate that repeated exposures to the same anxiogenic environment resulted in avoidance responses developing tolerance and approach responses developing sensitization. They suggest that tolerance and sensitization are two opposite sides of the habituation process to the same stimulus and may account for the maintained state of anxiety.
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12
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Sullivan R, Duchesne A, Hussain D, Waldron J, Laplante F. Effects of unilateral amygdala dopamine depletion on behaviour in the elevated plus maze: Role of sex, hemisphere and retesting. Behav Brain Res 2009; 205:115-22. [DOI: 10.1016/j.bbr.2009.07.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 07/14/2009] [Accepted: 07/19/2009] [Indexed: 10/20/2022]
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Roy V, Chapillon P, Jeljeli M, Caston J, Belzung C. Free versus forced exposure to an elevated plus-maze: evidence for new behavioral interpretations during test and retest. Psychopharmacology (Berl) 2009; 203:131-41. [PMID: 18998112 DOI: 10.1007/s00213-008-1378-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2008] [Accepted: 10/13/2008] [Indexed: 10/21/2022]
Abstract
RATIONALE The rodent elevated plus-maze is based on an approach/avoidance conflict between secure closed arms and aversive open arms that can be measured to assess anxiety. Despite this apparent simplicity, several discrepancies emerge from the interpretation of an animal's behavior in the maze, especially when considering the one-trial tolerance effect. OBJECTIVES AND METHODS In order to bring new elements of interpretation, we compared the behavior of rats exposed to the standard version of the test (forced exposure) to the behavior of rats that were allowed to freely explore the apparatus. We also compared the effects of testing/retesting and chlordiazepoxide in these two situations. RESULTS Our results confirm that open-arm avoidance is a natural tendency and therefore that it is not learned during initial exposure to the maze. In addition, comparison of the two situations suggests that some of the open-arm entries during a forced confrontation with the maze are better interpreted as attempts to avoid the whole situation, rather than as indications of a low level of anxiety. Finally, the one-trial tolerance effect was partially reduced in the free-exposure situation. CONCLUSIONS Our results contradict the hypothesis that there is acquisition of a phobic-like response to open arms during trial 1. Rather, they are discussed in line with the hypotheses by Rodgers and Shepherd (Psychopharmacology (Berl) 113:237-242, 1993) and Bertoglio and Carobrez (Behav Brain Res 108:197-203, 2000) concerning the acquisition of spatial information about the whole apparatus, leading on trial 2 to an unbalanced approach/avoidance conflict and to the inefficiency of anxiolytic drugs.
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Affiliation(s)
- Vincent Roy
- UPRES PSY-NCA, EA4306, Laboratoire de Psychologie et Neurosciences de la Cognition et de l'Affectivité, European Institute for Peptide Research (IFRMP 23), Université de Rouen, 76821, Mont-Saint-Aignan, Cedex, France.
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Petit-Demoulière B, Hascoët M, Bourin M. Factors triggering abolishment of benzodiazepines effects in the Four-Plate Test--retest in mice. Eur Neuropsychopharmacol 2008; 18:41-7. [PMID: 17544259 DOI: 10.1016/j.euroneuro.2007.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 03/28/2007] [Accepted: 04/24/2007] [Indexed: 11/23/2022]
Abstract
Abolishment of anxiolytic-like effects of diazepam occurs during re-exposure to some animal tests of anxiety. We investigated the loss of anxiolytic-like effects of diazepam during Trial 2 on previously undrugged mice, namely one-trial tolerance (OTT). Swiss mice were subjected to 1) Four-Plate Test (FPT) without punishments in Trial 1 or 2) FPT without punishments in both Trials or 3) FPT with spatial modifications in Trial 1 or 4) Elevated Plus Maze (EPM), then 24 h later to FPT, with saline, diazepam (1 mg/kg) or DOI (1 mg/kg). Removing punishments in Trial 1 does not counteract the effect reduction of diazepam in Trial 2, but spatial modifications of the aversive environment. Previous exposure to EPM does not trigger a loss of efficacy of diazepam in FPT. Electric punishments do not trigger OTT to benzodiazepines; whilst knowledge of the environment seems to be responsible for this phenomenon. FPT may be useful to study OTT because punishments potentate OTT in this model of anxiety.
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Affiliation(s)
- B Petit-Demoulière
- EA 3256 Neurobiologie de l'anxiété et de la dépression, Faculté de Médecine, BP 53508, 1 Rue Gaston Veil, F44035 Nantes Cedex 01 France
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15
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Vargas KM, Da Cunha C, Andreatini R. Amphetamine and pentylenetetrazole given post-trial 1 enhance one-trial tolerance to the anxiolytic effect of diazepam in the elevated plus-maze in mice. Prog Neuropsychopharmacol Biol Psychiatry 2006; 30:1394-402. [PMID: 16828217 DOI: 10.1016/j.pnpbp.2006.05.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Revised: 05/12/2006] [Accepted: 05/12/2006] [Indexed: 11/20/2022]
Abstract
There are several hypotheses to explain the lack of an anxiolytic effect on animals with previous maze experience (one-trial tolerance). Some of these hypotheses are related to learning and memory, so the reduction of trial 1 duration to 1 min or amnesic drug administration before trial 1 prevents the lack of an anxiolytic effect in trial 2. Amphetamine and pentylenetetrazole have been shown to enhance memory consolidation when administered immediately after training. Thus, the aim of the present study was to evaluate the effect of amphetamine (1.0-3.0 mg/kg) or pentylenetetrazole (30.0 mg/kg), at putative memory-enhancing doses, on the effect of diazepam (2.5 mg/kg) in the elevated plus-maze trial 2 on mice exposed to a 1-min long trial 1. Mice were submitted to 1-min trial 1 in the elevated plus-maze immediately followed by drug treatment (saline, amphetamine, or pentylenetetrazole) and to elevated plus-maze trial 2 after 48 h. Animals were treated with vehicle or diazepam 30 min before trial 2. The results showed that post-trial 1 saline and 1.0 mg/kg amphetamine did not induce one-trial tolerance. On the other hand, 2.0 and 3.0 mg/kg amphetamine and 30 mg/kg pentylenetetrazole induced a lack of anxiolytic effect of diazepam on trial 2 even with 1-min trial 1 length. Furthermore, these data were not due to novelty exposure in trial 1 or to amphetamine treatment so that mice exposed to an activity chamber instead of the plus-maze (trial 1) and then immediately submitted to amphetamine treatment (2.0 mg/kg) did not show one-trial tolerance 48 h after trial 1. Taken as a whole, these data support the hypothesis that memory is involved in the lack of an anxiolytic effect in the elevated plus-maze trial 2.
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Affiliation(s)
- Kleber Meneghel Vargas
- Laboratório de Fisiologia e Farmacologia do Sistema Nervoso Central, Departamento de Farmacologia, Setor de Ciências Biológicas, Universidade Federal do Paraná, Centro Politécnico, CP 19031, Curitiba, PR 81531-990, Brazil
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16
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Patti CL, Kameda SR, Carvalho RC, Takatsu-Coleman AL, Lopez GB, Niigaki ST, Abílio VC, Frussa-Filho R, Silva RH. Effects of morphine on the plus-maze discriminative avoidance task: role of state-dependent learning. Psychopharmacology (Berl) 2006; 184:1-12. [PMID: 16341847 DOI: 10.1007/s00213-005-0238-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Accepted: 10/20/2005] [Indexed: 10/25/2022]
Abstract
RATIONALE The amnesic effects of morphine may be related to its action on nociception, anxiety, or locomotion. This effect is also suggested to be related to state dependency. OBJECTIVES The aims of this study were to verify the effects of morphine on mice tested in the plus-maze discriminative avoidance task (DAT) that uses light and noise as aversive stimuli and allows the concomitant evaluation of learning, memory, anxiety, and locomotion and also to verify the possible role of state-dependent learning in the effects of morphine. METHODS AND RESULTS The DAT was conducted in a modified elevated plus-maze. In the training, the aversive stimuli were applied when mice entered in one of the enclosed arms, whereas in the test, no stimuli were applied. The main results showed that (1) pretraining morphine (5-20 mg/kg i.p.) induced retrieval deficits (evaluated by the time spent in the aversive arm in the test) but not acquisition deficits (evaluated by the decrease in aversive arm exploration along the training); (2) pretest morphine (5-10 but not 20 mg/kg) counteracted this deficit; (3) morphine induced hypolocomotion (decreased number of entries in the arms), irrespective of memory alterations; and (4) morphine did not alter anxiety-like behavior (evaluated by the time spent in the open arms) during the training. CONCLUSIONS Morphine given before training induces retrieval deficits in mice tested in the DAT, and these deficits could be related to morphine-induced state-dependent learning. Neither the memory deficit induced by pretraining morphine nor the reversal of this deficit by pretest morphine seems to be related to anxiety levels or locomotor alterations.
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Affiliation(s)
- C L Patti
- Department of Pharmacology, Universidade Federal de São Paulo, Rua Botucatu, 862-Ed. Leal Prado, 04023-062 São Paulo, Brazil
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Castro JPMV, Frussa-Filho R, Fukushiro DF, Chinen CC, Abílio VC, Silva RH. Effects of long-term continuous exposure to light on memory and anxiety in mice. Physiol Behav 2005; 86:218-23. [PMID: 16083922 DOI: 10.1016/j.physbeh.2005.07.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 06/07/2005] [Accepted: 07/12/2005] [Indexed: 11/29/2022]
Abstract
The studies on the relationship between the light/dark cycle and memory function mostly used protocols of acute disruption of the circadian rhythm. The aim of the present study is to verify the effects of long-term continuous exposure to light on memory, anxiety and motor parameters of mice tested in the plus-maze discriminative avoidance task. Mice were conditioned to choose between the two enclosed arms (one aversive and one non-aversive) while avoiding the open arms of a modified elevated plus-maze apparatus. Memory was evaluated by the time spent in the aversive enclosed arm, anxiety was evaluated by the time spent in the open arms and locomotor behavior was evaluated by number of entries in the arms of the maze. The results showed that long-term (35-42 days) continuous light exposure did not modify memory or anxiety parameters but increased locomotor activity. While the increase in locomotor behavior is in line with previous studies, the unexpected absence of alterations in memory and anxiety (reported to be influenced by the circadian rhythm) is discussed.
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Affiliation(s)
- J P M V Castro
- Departamento de Farmacologia, Universidade Federal de São Paulo, Brazil
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18
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Carobrez AP, Bertoglio LJ. Ethological and temporal analyses of anxiety-like behavior: the elevated plus-maze model 20 years on. Neurosci Biobehav Rev 2005; 29:1193-205. [PMID: 16084592 DOI: 10.1016/j.neubiorev.2005.04.017] [Citation(s) in RCA: 671] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2004] [Revised: 04/19/2005] [Accepted: 04/19/2005] [Indexed: 12/16/2022]
Abstract
As well as being considered a reliable measurement instrument of animal anxiety-like behavior, the elevated plus-maze (EPM) is also used as a post-hoc test to evaluate emotionality in genetically modified rodents. The present review considers factors which may further improve the validity (predictive/face/construct) of the EPM model: (1) the importance of measuring defensive patterns of response such as risk assessment in addition to traditional measures such as open arm time; (2) other methodological refinements such as min-by-min scoring and use of a test/retest protocol; and (3) the identification and control of major sources of variability in this test. To estimate whether current use of the EPM by researchers takes the above factor into account, a survey of the recent literature was conducted. Results showed that the majority of studies have not yet assimilated these important considerations into their use of the EPM. For example, although risk assessment measures may be more sensitive to anxiety modulating drugs than traditional measures, only a quarter of studies have adopted them. It is hoped that this review can provide insights into the optimal use of the EPM, a simple task that can be very complex in terms of behavioral analysis.
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Affiliation(s)
- A P Carobrez
- Departamento de Farmacologia, CCB, Universidade Federal de Santa Catarina, Florianópolis, SC, 88049-900, Brazil.
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Bessa JM, Oliveira M, Cerqueira JJ, Almeida OFX, Sousa N. Age-related qualitative shift in emotional behaviour: Paradoxical findings after re-exposure of rats in the elevated-plus maze. Behav Brain Res 2005; 162:135-42. [PMID: 15922074 DOI: 10.1016/j.bbr.2005.03.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Revised: 03/10/2005] [Accepted: 03/13/2005] [Indexed: 10/25/2022]
Abstract
Several variables, including age, are known to influence anxiety. Previous exposure to the elevated-plus maze (EPM) is known to modify emotional behaviour as retesting in the EPM at a standard age of 3 months increases open-arm avoidance and attenuates the effects of anxiolytic drugs. This study analysed whether similar results are obtained when older animals are subjected to these experimental paradigms. Overall, increasing age was associated with more signs of anxiety. Additionally, we observed a paradoxical behaviour pattern in aged-subjects that were re-exposed to the EPM, with mid-aged and old rats failing to display open arm avoidance (OAA) in the second trial; this qualitative shift in emotional behaviour was not associated with decreased locomotion. An examination of how age influences responsiveness to anxiolytic drugs, with or without previous maze experience, was also conducted. Midazolam (0.5 and 1 mg/kg) proved anxiolytic in maize-naive young animals; in marked contrast, in older animals midazolam at 1 mg/kg resulted in sedation but not anxiolyis. One trial tolerance to midazolam was evident in animals of both ages that were subjected to a second EPM trial; the latter phenomenon was apparently accentuated in older animals as they do not show open arm avoidance upon re-exposure to the EPM. These data suggest that the age-associated 'resistance' to anxiolytic drugs might be related to a qualitative shift in emotional behaviour.
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Affiliation(s)
- J M Bessa
- Neuroscience Group, Life and Health Science Research Institute (ICVS), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
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20
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Bertoglio LJ, Anzini C, Lino-de-Oliveira C, Carobrez AP. Enhanced dorsolateral periaqueductal gray activity counteracts the anxiolytic response to midazolam on the elevated plus-maze Trial 2 in rats. Behav Brain Res 2005; 162:99-107. [PMID: 15922070 DOI: 10.1016/j.bbr.2005.03.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 03/04/2005] [Accepted: 03/07/2005] [Indexed: 10/25/2022]
Abstract
Rodents previously (Trial 1) experienced in the elevated plus-maze (EPM) apparatus no longer respond to anxiolytic-like drugs during retesting (Trial 2). In view of the fact that the dorsolateral periaqueductal gray (dlPAG) modulates fear/anxiety-like behavior, the present study sought to determine its role in this phenomenon. In order to address this issue, EPM-experienced rats that had received lidocaine, a drug which produces a reversible functional deactivation, intra-dlPAG pre-Trial 1, post-Trial 1 or pre-Trial 2, were systemically injected with the benzodiazepine midazolam and submitted to the EPM apparatus. According to the results, 0.25 mg/kg midazolam increased open arms exploration and reduced risk assessment behavior, suggesting an anxiolytic-like effect in EPM-naive rats, regardless of the intra-dlPAG treatment. EPM-experienced rats administered with midazolam only displayed a similar pattern of behavior when lidocaine was administered intra-dlPAG pre-Trial 2, but not pre- or post-Trial 1. These effects were observed in the absence of changes in enclosed arms entries, an EPM general exploratory activity index. The present results suggest that an increased activity of the dlPAG during Trial 2 would explain the lack of anxiolytic-like effect of drugs elicited by prior EPM test experience.
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Affiliation(s)
- Leandro José Bertoglio
- Departamento de Farmacologia, FMRP-USP, Av. Bandeirantes, 3900, Ribeirão Preto, SP 14049-900, Brazil
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21
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Calzavara MB, Patti CL, Lopez GB, Abílio VC, Silva RH, Frussa-Filho R. Role of learning of open arm avoidance in the phenomenon of one-trial tolerance to the anxiolytic effect of chlordiazepoxide in mice. Life Sci 2005; 76:2235-46. [PMID: 15733938 DOI: 10.1016/j.lfs.2004.10.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 10/23/2004] [Indexed: 11/26/2022]
Abstract
A single exposure to the elevated plus-maze (EPM) test of anxiety reduces or abolishes the anxiolytic efficacy of benzodiazepines on a second trial. Some possible explanations to the occurrence of this phenomenon (one-trial tolerance-OTT) involve behavioral modifications thought to be consequence of some kind of learning in the first trial. In the present study, the influence of learning-impairing situations on the effects of the benzodiazepine chlordiazepoxide on mice re-tested in the EPM is investigated. The results showed that: (1) as expected, the administration of chlordiazepoxide to mice re-tested in the EPM- under the same conditions of the first trial- failed to induce anxiolysis; (2) a decreased percent time in the open arms was observed on the second trial of mice exposed to both trials under the same experimental conditions; (3) neither the increase in open arm avoidance by mice re-exposed to the EPM nor the OTT to chlordiazepoxide effect were modified by administration of the amnestic agent scopolamine; (4) the decrement of the duration of the first trial to 1 min or the change in light and noise conditions in both trials counteracted the increase in open arm avoidance on trial 2; (5) none of the later procedures modified the phenomenon of OTT. Although not discarding the modulation exerted by other memory processes in the OTT phenomenon, the results indicate that situations that impair the learned avoidance response to the open arms in the EPM do not modify the phenomenon of OTT.
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Affiliation(s)
- M B Calzavara
- Departamento de Farmacologia, Universidade Federal de São Paulo, Rua Botucatu 862, Edifício José Leal Prado, CEP 04023-062, São Paulo, SP, Brazil
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22
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Silva RH, Kameda SR, Carvalho RC, Takatsu-Coleman AL, Niigaki ST, Abílio VC, Tufik S, Frussa-Filho R. Anxiogenic effect of sleep deprivation in the elevated plus-maze test in mice. Psychopharmacology (Berl) 2004; 176:115-22. [PMID: 15160262 DOI: 10.1007/s00213-004-1873-z] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Accepted: 03/05/2004] [Indexed: 11/24/2022]
Abstract
RATIONALE Several clinical studies demonstrate that the absence of periods of sleep is closely related to occurrence of anxiety symptoms. However, the basis of these interactions is poorly understood. Studies performed with animal models of sleep deprivation and anxiety would be helpful in the understanding of the mechanisms underlying this relationship, but some animal studies have not corroborated clinical data, reporting anxiolytic effects of sleep deprivation. OBJECTIVES The aim of the present study was to verify the effects of different protocols of sleep deprivation in mice tested in the elevated plus-maze and to assess the effect of chlordiazepoxide and clonidine. METHODS Three-month-old male mice were sleep-deprived for 24 or 72 h using the methods of single or multiple platforms in water tanks. Mice kept in their home cages were used as controls. Plus-maze behavior was observed immediately after the deprivation period. RESULTS Mice that were sleep-deprived for 72 h spent a lower percent time in the open arms of the apparatus than control animals. This sleep deprivation-induced anxiety-like behavior was unaffected by treatment with chlordiazepoxide (5.0 and 7.5 mg/kg IP), but reversed by an administration of 5 or 10 microg/kg IP clonidine. CONCLUSION The results indicate that under specific methodological conditions sleep deprivation causes an increase in anxiety-like behavior in mice exposed to the elevated plus-maze.
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Affiliation(s)
- Regina H Silva
- Departamento de Farmacolgia, Universidade Federal de São Paulo, Rua Botucatu, 862, Edifício Leal Prado, Sao Paulo, SP, Brazil.
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Bertoglio LJ, Carobrez AP. Scopolamine given pre-Trial 1 prevents the one-trial tolerance phenomenon in the elevated plus-maze Trial 2. Behav Pharmacol 2004; 15:45-54. [PMID: 15075626 DOI: 10.1097/00008877-200402000-00006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A learned avoidance response has been one of the hypotheses proposed to explain the 'one-trial tolerance' (OTT) phenomenon, which represents a drug's loss of anxiolytic-like effect in the elevated plus-maze (EPM) test in experienced rodents. Based on these facts, if some kind of learning occurs throughout Trial 1, then an impairment of its acquisition would maintain the drug's anxiolytic-like effect on Trial 2. Using male Wistar rats, the present study examined whether scopolamine (SCO; 0.5-1.5 mg/kg), a drug that impairs learning acquisition, given 30 min prior to Trial 1, actually prevents the OTT phenomenon to either the midazolam (MDZ; 0.5 mg/kg) or the memantine (MEM; 8.0 mg/kg) anxiolytic-like effect on the EPM Trial 2 (48 h later). According to the results, both MDZ and MEM increased open-arm exploration (indicating anxiolysis) on Trial 2 only in rats that had been treated previously with 1.5 mg/kg SCO. These results were observed in the absence of change in general exploratory activity. The present findings suggest that SCO impaired the acquisition of the behavioral strategy to cope with the subsequent EPM exposure that supposedly underlies the OTT phenomenon, thereby revealing the anxiolytic-like effects of MDZ and MEM on Trial 2.
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Affiliation(s)
- L J Bertoglio
- Departamento de Farmacologia, CCB, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
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24
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Bertoglio LJ, Carobrez AP. Anxiolytic-like effects of NMDA/glycine-B receptor ligands are abolished during the elevated plus-maze trial 2 in rats. Psychopharmacology (Berl) 2003; 170:335-42. [PMID: 13680083 DOI: 10.1007/s00213-003-1558-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 06/04/2003] [Indexed: 10/26/2022]
Abstract
RATIONALE Drugs enhancing the GABA(A) and/or reducing the NMDA/glycine-B receptor activity produce an anxiolytic effect. Regarding the former drugs (e.g. benzodiazepines), prior elevated plus-maze (EPM) test experience abolishes the trial 2 anxiolytic activity, a phenomenon referred to as "one-trial tolerance" (OTT). OBJECTIVES The present study examined whether the OTT phenomenon occurs with drugs that reduce the NMDA/glycine-B receptor activity. METHODS Maze-naive and maze-experienced (prior EPM exposure) rats were treated with (+/-)-HA-966 (2.0 or 4.0 mg/kg), (+)-MK-801 (0.03 or 0.06 mg/kg) or memantine (4.0 or 8.0 mg/kg) and submitted to the EPM. To investigate whether the loss of drug responsiveness was due to pharmacological tolerance, rats received memantine (8.0 mg/kg) both 48 h and 30 min before the first EPM exposure. RESULTS All drugs increased open arms exploration, indicating an anxiolytic effect, in maze-naive but not in maze-experienced rats, in which increased open arms avoidance was observed. An anxiolytic effect was also observed after repeated memantine administration in maze-naive/drug-experienced rats. These effects were observed in the absence of changes in enclosed arms entries, an EPM general exploratory activity index. CONCLUSIONS The present findings extend the OTT phenomenon to drugs that reduce the NMDA/glycine-B-receptor activity, and emphasize the repeated test exposure rather than repeated drug administration as a critical determinant for the drug anxiolytic activity. Considering the mechanisms by which the EPM experience alters the drug effects, the present findings favor the hypothesis in which the OTT phenomenon emerge as a consequence of the development and adoption of an anxiolytic-insensitive behavioral strategy.
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Affiliation(s)
- Leandro J Bertoglio
- Departamento de Farmacologia, CCB, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina, Brazil
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Dal-Cól MLC, Pereira LO, Rosa VP, Calixto AV, Carobrez AP, Faria MS. Lack of midazolam-induced anxiolysis in the plus-maze Trial 2 is dependent on the length of Trial 1. Pharmacol Biochem Behav 2003; 74:395-400. [PMID: 12479960 DOI: 10.1016/s0091-3057(02)01009-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The influence of the first exposure length upon the effect of midazolam (MDZ) administration prior to the second exposure in the elevated plus-maze (EPM) was investigated. Drug-free rats were assigned to freely explore the EPM for 1, 2 or 5 min (Trial 1). Twenty-four hours later, each group was subdivided in two further groups, which were retested in the EPM for 5 min, 30 min after either saline or MDZ (1.5 mg kg(-1)) administration (Trial 2). The data showed that during Trial 2, the percentage of entries (%Open arm entries) and time spent in the open arms (%Open arm time) were decreased if rats were pre-exposed to the EPM for 2- or 5-min Trial 1, while the group submitted to 1-min Trial 1 length displayed decreased %Open arm time only. The anxiolytic effect of MDZ prior to Trial 2 was present in the group submitted to 1-min, impaired in the group submitted to 2-min and absent in the group submitted to 5-min Trial 1 length. Data are analyzed taking into account the emotional learning which underlies the exploratory behavior during the EPM Trial 2.
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Affiliation(s)
- M L C Dal-Cól
- Department of Physiological Sciences, Centre of Biological Sciences, Federal University of Santa Catarina, 88, 040-900, Florianópolis, SC, Brazil
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Silva RH, Frussa-Filho R. Naltrexone potentiates both amnestic and anxiolytic effects of chlordiazepoxide in mice. Life Sci 2002; 72:721-30. [PMID: 12467912 DOI: 10.1016/s0024-3205(02)02298-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Studies have suggested that opioid antagonists potentiate the anxiolytic effect but not the amnestic action of chlordiazepoxide (CDZ). We investigated the effects of naltrexone (NAL) on the anxiolytic and amnestic effects of CDZ in mice tested in the plus-maze discriminative avoidance task (DAT). Mice are conditioned to choose between two enclosed arms (one of which aversive) while avoiding the two open arms of the apparatus. This task measures memory (time spent in the aversive vs. time in the non-aversive enclosed arms) and anxiety (time spent in the open arms). Mice treated with saline (SAL) or 5 mg/kg NAL, and SAL or 2.5 mg/kg CDZ were submitted to DAT training. The test was performed 24 h later, without aversive stimuli. In the training, NAL + CDZ group showed higher percent time spent in the open arms than all the other groups. In the test, NAL + CDZ (but not SAL + CDZ) group showed higher percent time spent in the aversive enclosed arm than SAL + SAL and NAL + SAL groups. The data suggest that NAL potentiates the small decreases in anxiety and retention induced by a subeffective dose of CDZ.
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Affiliation(s)
- Regina H Silva
- Department of Pharmacology, Universidade Federal de São Paulo, Rua Botucatu, 862, Brazil
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