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Bacteria affect Caenorhabditis elegans responses to MeHg toxicity. Neurotoxicology 2019; 75:129-135. [PMID: 31542475 DOI: 10.1016/j.neuro.2019.09.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 09/02/2019] [Indexed: 01/06/2023]
Abstract
The organic form of mercurial complex, methylmercury (MeHg), is a neurotoxin that bioaccumulates in the food web. Studies in model organisms, such as Caenorhabditis elegans (C. elegans), provide powerful insights on the role of genetic factors in MeHg-induced toxicity. C. elegans is a free living worm that is commonly cultured in nematode growth medium (NGM) agar plates seeded with bacteria. The bacteria have broad impact on C. elegans biology, including development, reproduction and lifespan, as well as metabolism of experimental chemicals. We hypothesized that MeHg toxicity in C. elegans could be modified by the bacterial food. Using a C. elegans wild-type (WT) strain and transgenic reporter strains, we found that bacterial food reduced the chronic toxicity of MeHg in C. elegans in a dose- and live-status-dependent manner. The MeHg-induced death rate in C. elegans was highest in fasted worms, followed by dehydrated dead bacteria, dead bacteria and live bacteria fed worms. Among the different bacterial foods, dehydrated dead bacteria fed worms were most sensitive to the toxicity of MeHg. The distinct bacteria food (dehydrated dead bacteria food) attenuated oxidative stress and development delay in C. elegans exposed to MeHg. The FOXO transcriptional factor DAF16 was not changed by MeHg but modified by the distinct bacteria food. Independent of MeHg treatment, daf-16 expression in fed worms migrated from the intestine to muscle. We conclude that, in chronic exposure studies in C. elegans, the effects of bacteria on toxicological outcomes should be considered.
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Pereira P, Korbas M, Pereira V, Cappello T, Maisano M, Canário J, Almeida A, Pacheco M. A multidimensional concept for mercury neuronal and sensory toxicity in fish - From toxicokinetics and biochemistry to morphometry and behavior. Biochim Biophys Acta Gen Subj 2019; 1863:129298. [PMID: 30768958 DOI: 10.1016/j.bbagen.2019.01.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 01/16/2019] [Accepted: 01/30/2019] [Indexed: 12/14/2022]
Abstract
BACKGROUND Neuronal and sensory toxicity of mercury (Hg) compounds has been largely investigated in humans/mammals with a focus on public health, while research in fish is less prolific and dispersed by different species. Well-established premises for mammals have been governing fish research, but some contradictory findings suggest that knowledge translation between these animal groups needs prudence [e.g. the relative higher neurotoxicity of methylmercury (MeHg) vs. inorganic Hg (iHg)]. Biochemical/physiological differences between the groups (e.g. higher brain regeneration in fish) may determine distinct patterns. This review undertakes the challenge of identifying sensitive cellular targets, Hg-driven biochemical/physiological vulnerabilities in fish, while discriminating specificities for Hg forms. SCOPE OF REVIEW A functional neuroanatomical perspective was conceived, comprising: (i) Hg occurrence in the aquatic environment; (ii) toxicokinetics on central nervous system (CNS)/sensory organs; (iii) effects on neurotransmission; (iv) biochemical/physiological effects on CNS/sensory organs; (v) morpho-structural changes on CNS/sensory organs; (vi) behavioral effects. The literature was also analyzed to generate a multidimensional conceptualization translated into a Rubik's Cube where key factors/processes were proposed. MAJOR CONCLUSIONS Hg neurosensory toxicity was unequivocally demonstrated. Some correspondence with toxicity mechanisms described for mammals (mainly at biochemical level) was identified. Although the research has been dispersed by numerous fish species, 29 key factors/processes were pinpointed. GENERAL SIGNIFICANCE Future trends were identified and translated into 25 factors/processes to be addressed. Unveiling the neurosensory toxicity of Hg in fish has a major motivation of protecting ichtyopopulations and ecosystems, but can also provide fundamental knowledge to the field of human neurodevelopment.
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Affiliation(s)
- Patrícia Pereira
- Department of Biology and CESAM, University of Aveiro, Aveiro 3810-193, Portugal
| | - Malgorzata Korbas
- Science Division, Canadian Light Source Inc., Saskatoon, Canada; Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Canada
| | - Vitória Pereira
- Department of Biology and CESAM, University of Aveiro, Aveiro 3810-193, Portugal
| | - Tiziana Cappello
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale F. Stagno d'Alcontres 31, Messina 98166, Italy
| | - Maria Maisano
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale F. Stagno d'Alcontres 31, Messina 98166, Italy
| | - João Canário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1049-001, Portugal
| | - Armando Almeida
- Life and Health Sciences Research Institute (ICVS), School of Medicine (EM), University of Minho, Campus of Gualtar, Braga 4750-057, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Portugal
| | - Mário Pacheco
- Department of Biology and CESAM, University of Aveiro, Aveiro 3810-193, Portugal.
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Puga S, Cardoso V, Pinto-Ribeiro F, Pacheco M, Almeida A, Pereira P. Brain morphometric profiles and their seasonal modulation in fish (Liza aurata) inhabiting a mercury contaminated estuary. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 237:318-328. [PMID: 29499575 DOI: 10.1016/j.envpol.2018.02.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/09/2018] [Accepted: 02/16/2018] [Indexed: 06/08/2023]
Abstract
Mercury (Hg) is a potent neurotoxicant known to induce important adverse effects on fish, but a deeper understanding is lacking regarding how environmental exposure affects the brain morphology and neural plasticity of specific brain regions in wild specimens. In this work, it was evaluated the relative volume and cell density of the lateral pallium, hypothalamus, optic tectum and molecular layer of the cerebellum on wild Liza aurata captured in Hg-contaminated (LAR) and non-contaminated (SJ) sites of a coastal system (Ria de Aveiro, Portugal). Given the season-related variations in the environment that fish are naturally exposed, this assessment was performed in the winter and summer. Hg triggered a deficit in cell density of hypothalamus during the winter that could lead to hormonal dysfunctions, while in the summer Hg promoted larger volumes of the optic tectum and cerebellum, indicating the warm period as the most critical for the manifestation of putative changes in visual acuity and motor-dependent tasks. Moreover, in fish from the SJ site, the lateral pallium relative volume and the cell density of the hypothalamus and optic tectum were higher in the winter than in summer. Thus, season-related stimuli strongly influence the size and/or cell density of specific brain regions in the non-contaminated area, pointing out the ability of fish to adapt to environmental and physiological demands. Conversely, fish from the Hg-contaminated site showed a distinct seasonal profile of brain morphology, presenting a larger optic tectum in the summer, as well as a larger molecular layer of the cerebellum with higher cell density. Moreover, Hg exposure impaired the winter-summer variation of the lateral pallium relative size (as observed at SJ). Altogether, seasonal variations in fish neural morphology and physiology should be considered when performing ecotoxicological studies in order to better discriminate the Hg neurotoxicity.
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Affiliation(s)
- Sónia Puga
- Life and Health Sciences Research Institute (ICVS), School of Medicine (EM), Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Vera Cardoso
- Life and Health Sciences Research Institute (ICVS), School of Medicine (EM), Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Filipa Pinto-Ribeiro
- Life and Health Sciences Research Institute (ICVS), School of Medicine (EM), Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Mário Pacheco
- Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
| | - Armando Almeida
- Life and Health Sciences Research Institute (ICVS), School of Medicine (EM), Campus of Gualtar, University of Minho, 4750-057 Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| | - Patrícia Pereira
- Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
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Geier MC, James Minick D, Truong L, Tilton S, Pande P, Anderson KA, Teeguardan J, Tanguay RL. Systematic developmental neurotoxicity assessment of a representative PAH Superfund mixture using zebrafish. Toxicol Appl Pharmacol 2018; 354:115-125. [PMID: 29630969 DOI: 10.1016/j.taap.2018.03.029] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/16/2018] [Accepted: 03/26/2018] [Indexed: 02/06/2023]
Abstract
Superfund sites often consist of complex mixtures of polycyclic aromatic hydrocarbons (PAHs). It is widely recognized that PAHs pose risks to human and environmental health, but the risks posed by exposure to PAH mixtures are unclear. We constructed an environmentally relevant PAH mixture with the top 10 most prevalent PAHs (SM10) from a Superfund site derived from environmental passive sampling data. Using the zebrafish model, we measured body burden at 48 hours post fertilization (hpf) and evaluated the developmental and neurotoxicity of SM10 and the 10 individual constituents at 24 hours post fertilization (hpf) and 5 days post fertilization (dpf). Zebrafish embryos were exposed from 6 to 120 hpf to (1) the SM10 mixture, (2) a variety of individual PAHs: pyrene, fluoranthene, retene, benzo[a]anthracene, chrysene, naphthalene, acenaphthene, phenanthrene, fluorene, and 2-methylnaphthalene. We demonstrated that SM10 and only 3 of the individual PAHs were developmentally toxic. Subsequently, we constructed and exposed developing zebrafish to two sub-mixtures: SM3 (comprised of 3 of the developmentally toxicity PAHs) and SM7 (7 non-developmentally toxic PAHs). We found that the SM3 toxicity profile was similar to SM10, and SM7 unexpectedly elicited developmental toxicity unlike that seen with its individual components. The results demonstrated that the overall developmental toxicity in the mixtures could be explained using the general concentration addition model. To determine if exposures activated the AHR pathway, spatial expression of CYP1A was evaluated in the 10 individual PAHs and the 3 mixtures at 5 dpf. Results showed activation of AHR in the liver and vasculature for the mixtures and some individual PAHs. Embryos exposed to SM10 during development and raised in chemical-free water into adulthood exhibited decreased learning and responses to startle stimulus indicating that developmental SM10 exposures affect neurobehavior. Collectively, these results exemplify the utility of zebrafish to investigate the developmental and neurotoxicity of complex mixtures.
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Affiliation(s)
- Mitra C Geier
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States
| | - D James Minick
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States
| | - Lisa Truong
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States
| | - Susan Tilton
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States
| | - Paritosh Pande
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Kim A Anderson
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States
| | - Justin Teeguardan
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Robert L Tanguay
- Department of Environmental and Molecular Toxicology, Oregon State University, ALS 1007, Corvallis, OR 97331, United States.
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Naderi M, Salahinejad A, Jamwal A, Chivers DP, Niyogi S. Chronic Dietary Selenomethionine Exposure Induces Oxidative Stress, Dopaminergic Dysfunction, and Cognitive Impairment in Adult Zebrafish (Danio rerio). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:12879-12888. [PMID: 28981273 DOI: 10.1021/acs.est.7b03937] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The present study was designed to investigate the effects of chronic dietary exposure to selenium (Se) on zebrafish cognition and also to elucidate possible mechanism(s) by which Se exerts its neurotoxicity. To this end, adult zebrafish were exposed to different concentrations of dietary l-selenomethionine (control, 2.3, 9.7, 32.5, or 57.7 μg Se/g dry weight) for 30 days. Cognitive performance of fish was tested using a latent learning paradigm in a complex maze. In addition, we also evaluated oxidative stress biomarkers and the expression of genes involved in dopaminergic neurotransmission in the zebrafish brain. Fish treated with higher dietary Se doses (32.5 and 57.5 μg Se/g) exhibited impaired performance in the latent learning task. The impaired learning was associated with the induction of oxidative stress and altered mRNA expression of dopamine receptors, tyrosine hydroxylase, and dopamine transporter genes in the zebrafish brain. Collectively, our results illustrate that cognitive impairment in zebrafish could be associated with Se-induced oxidative stress and altered dopaminergic neurotransmission in the brain.
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Affiliation(s)
- Mohammad Naderi
- Department of Biology, University of Saskatchewan , 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Arash Salahinejad
- Department of Biology, University of Saskatchewan , 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Ankur Jamwal
- Department of Biology, University of Saskatchewan , 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Douglas P Chivers
- Department of Biology, University of Saskatchewan , 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Som Niyogi
- Department of Biology, University of Saskatchewan , 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
- Toxicology Centre, University of Saskatchewan , 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
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Knecht AL, Truong L, Simonich MT, Tanguay RL. Developmental benzo[a]pyrene (B[a]P) exposure impacts larval behavior and impairs adult learning in zebrafish. Neurotoxicol Teratol 2017; 59:27-34. [PMID: 27989697 PMCID: PMC5235990 DOI: 10.1016/j.ntt.2016.10.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 10/18/2016] [Accepted: 10/21/2016] [Indexed: 12/23/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are produced from incomplete combustion of organic materials or fossil fuels, and are present in crude oil and coal; therefore, they are ubiquitous environmental contaminants present in urban air, dust, soil, and water. It is widely recognized that PAHs pose risks to human health, especially for the developing fetus and infant where PAH exposures have been linked to in-utero mortality, cardiovascular effects, and lower intelligence. Using the zebrafish model, we evaluated the developmental toxicity of benzo[a]pyrene (B[a]P). Zebrafish embryos were exposed from 6 to 120h post fertilization (hpf) to 0.4 and 4μM B[a]P. The Viewpoint Zebrabox systems were used to evaluate larval photomotor response (LPR) activity and we identified that exposure to 4μM B[a]P resulted in a hyperactive LPR phenotype. To evaluate the role of aryl hydrocarbon receptor (AHR) in this larval phenotype, we exposed ahr2hu2334 null larvae to 4μM B[a]P. Though ahr2hu2334 larvae did not display hyperactive swimming, these larvae had a decrease in LPR activity, suggesting that AHR2 plays a role in B[a]P induced larval hyperactivity. To determine if developmental B[a]P exposures would produce adult behavioral deficits, a subset of exposed animals was raised to adulthood and tested in a conditioned stimulus test using shuttleboxes. Developmentally exposed B[a]P zebrafish exhibited decreased learning and memory. Together this data demonstrates that developmental B[a]P exposure adversely impacts larval behavior, and learning in adult zebrafish.
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Affiliation(s)
- Andrea L Knecht
- Department of Environmental and Molecular Toxicology, Sinnhuber Aquatic Research Laboratory, Environmental Health Sciences Center, Oregon State University, Corvallis, OR, USA
| | - Lisa Truong
- Department of Environmental and Molecular Toxicology, Sinnhuber Aquatic Research Laboratory, Environmental Health Sciences Center, Oregon State University, Corvallis, OR, USA
| | - Michael T Simonich
- Department of Environmental and Molecular Toxicology, Sinnhuber Aquatic Research Laboratory, Environmental Health Sciences Center, Oregon State University, Corvallis, OR, USA
| | - Robert L Tanguay
- Department of Environmental and Molecular Toxicology, Sinnhuber Aquatic Research Laboratory, Environmental Health Sciences Center, Oregon State University, Corvallis, OR, USA.
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Lou D, Wang Q, Huang M, Zhou Z. Does age matter? Comparison of neurobehavioral effects of paraquat exposure on postnatal and adult C57BL/6 mice. Toxicol Mech Methods 2016; 26:667-673. [DOI: 10.1080/15376516.2016.1223241] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Dan Lou
- School of Public Health/MOE Key Lab of Public Health Safety/WHO Collaborating Center for Occupational Health, Fudan University, Shanghai, China
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China
| | - Qiaochu Wang
- School of Public Health/MOE Key Lab of Public Health Safety/WHO Collaborating Center for Occupational Health, Fudan University, Shanghai, China
| | - Min Huang
- Department of Environmental Health Science, School of Public Health, Ningxia Medical University, Yinchuan, China
| | - Zhijun Zhou
- School of Public Health/MOE Key Lab of Public Health Safety/WHO Collaborating Center for Occupational Health, Fudan University, Shanghai, China
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Singh P, Chowdhuri DK. Environmental Presence of Hexavalent but Not Trivalent Chromium Causes Neurotoxicity in Exposed Drosophila melanogaster. Mol Neurobiol 2016; 54:3368-3387. [DOI: 10.1007/s12035-016-9909-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 05/03/2016] [Indexed: 02/06/2023]
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Neurobehavioral impairments produced by developmental lead exposure persisted for generations in zebrafish (Danio rerio). Neurotoxicology 2016; 52:176-85. [DOI: 10.1016/j.neuro.2015.12.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/21/2015] [Accepted: 12/09/2015] [Indexed: 01/19/2023]
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Xu X, Weber D, Martin A, Lone D. Trans-generational transmission of neurobehavioral impairments produced by developmental methylmercury exposure in zebrafish (Danio rerio). Neurotoxicol Teratol 2016; 53:19-23. [DOI: 10.1016/j.ntt.2015.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/25/2015] [Accepted: 11/09/2015] [Indexed: 01/28/2023]
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A rapid throughput approach identifies cognitive deficits in adult zebrafish from developmental exposure to polybrominated flame retardants. Neurotoxicology 2014; 43:134-142. [PMID: 24674958 DOI: 10.1016/j.neuro.2014.03.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 03/13/2014] [Accepted: 03/13/2014] [Indexed: 12/18/2022]
Abstract
A substantial body of evidence has correlated the human body burdens of some polybrominated diphenyl ether (PBDE) flame retardants with cognitive and other behavioral deficits. Adult zebrafish exhibit testable learning and memory, making them an increasingly attractive model for neurotoxicology. Our goal was to develop a rapid throughput means of identifying the cognitive impact of developmental exposure to flame retardants in the zebrafish model. We exposed embryos from 6h post fertilization to 5 days post fertilization to either PBDE 47 (0.1μM), PBDE 99 (0.1μM) or PBDE 153 (0.1μM), vehicle (0.1% DMSO), or embryo medium (EM). The larvae were grown to adulthood and evaluated for the rate at which they learned an active-avoidance response in an automated shuttle box array. Zebrafish developmentally exposed to PBDE 47 learned the active avoidance paradigm significantly faster than the 0.1% DMSO control fish (P<0.0001), but exhibited significantly poorer performance when retested suggestive of impaired memory retention or altered neuromotor activity. Learning in the PBDE 153 group was not significantly different from the DMSO group. Developmental exposure to 0.1% DMSO impaired adult active avoidance learning relative to the sham group (n=39; P<0.0001). PBDE 99 prevented the DMSO effect, yielding a learning rate not significantly different from the sham group (n=36; P>0.9). Our results underscore the importance of vehicle choice in accurately assessing chemical effects on behavior. Active avoidance response in zebrafish is an effective model of learning that, combined with automated shuttle box testing, will provide a highly efficient platform for evaluating persistent neurotoxic hazard from many chemicals.
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Morin C, de Souza Silva MA, Müller CP, Hardigan P, Spieler RE. Active avoidance learning in zebrafish (Danio rerio)--the role of sensory modality and inter-stimulus interval. Behav Brain Res 2013; 248:141-3. [PMID: 23603556 DOI: 10.1016/j.bbr.2013.04.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
Abstract
The zebrafish (Danio rerio) promises to meet the growing need of a high throughput model in the fields of gerontological and neurobehavioral research by possessing highly conserved anatomy and physiology with vertebrates, while having low maintenance costs. Here we further explore the conditions of active avoidance learning in zebrafish. Two pairs of distinct aversive conditioning experiments using shuttle boxes were designed to compare the effects of sensory modality and conditioned-unconditioned stimulus interval (CS-US interval) upon memory formation and retention. We found that olfactory conditioning with phenylethyl alcohol as a CS was significantly more likely to produce a successful outcome than with a visual CS. Likewise a 10 s CS-US interval yielded significantly more successful memory formation than a 15 s interval. These conditions may further facilitate the use of zebrafish to explore the genetic and neuronal base of active avoidance learning and its neuropharmacological improvement.
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