title: Effects of low dose endosulfan exposure on brain neurotransmitter levels in the African clawed frog Xenopus laevis.
abstract: Understanding the impact of pesticides in amphibians is of growing concern to assess the causes of their decline. Among pesticides, endosulfan belongs to one of the potential sources of danger because of its wide use and known effects, particularly neurotoxic, on a variety of organisms. However, the effect of endosulfan was not yet evaluated on amphibians at levels encompassing simultaneously brain neurotransmitters and behavioural endpoints. In this context, tadpoles of the African clawed frog Xenopus laevis were submitted to four treatments during 27 d: one control, one ethanol control, and two low environmental concentrations of endosulfan (0.1 and 1 μg L(-1)). Endosulfan induced a significant increase of brain serotonin level at both concentrations and a significant increase of brain dopamine and GABA levels at the lower exposure but acetylcholinesterase activity was not modified by the treatment. The gene coding for the GABA transporter 1 was up-regulated in endosulfan contaminated tadpoles while the expression of other genes coding for the neurotransmitter receptors or for the enzymes involved in their metabolic pathways was not significantly modified by endosulfan exposure. Endosulfan also affected foraging, and locomotion in links with the results of the physiological assays, but no effects were seen on growth. These results show that low environmental concentrations of endosulfan can induce adverse responses in X. laevis tadpoles. At a broader perspective, this suggests that more research using and linking multiple markers should be used to understand the complex mode of action of pollutants.
authors.affiliation: Research Unit in Environmental and Evolutionary Biology, University of Namur, Belgium; Laboratory of Fish and Amphibian Ethology, Behavioural Biology Unit, Department of Biology, Ecology and Evolution, University of Liège, Belgium.
authors.forename: Valérie
authors.initials: V
authors.lastname: Preud'homme
authors.affiliation: Research Unit in Environmental and Evolutionary Biology, University of Namur, Belgium.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Milla
authors.affiliation: Research Unit in Environmental and Evolutionary Biology, University of Namur, Belgium.
authors.forename: Virginie
authors.initials: V
authors.lastname: Gillardin
authors.affiliation: Mass Spectrometry Laboratory, Department of Chemistry, GIGA, University of Liège, Belgium.
authors.forename: Edwin
authors.initials: E
authors.lastname: De Pauw
authors.affiliation: Laboratory of Fish and Amphibian Ethology, Behavioural Biology Unit, Department of Biology, Ecology and Evolution, University of Liège, Belgium.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Denoël
authors.affiliation: Research Unit in Environmental and Evolutionary Biology, University of Namur, Belgium. Electronic address: Patrick.kestemont@unamur.be.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kestemont
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004726:Endosulfan / Q000633:toxicity*; D005247:Feeding Behavior / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011897:Random Allocation; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D007306:Insecticides; D018377:Neurotransmitter Agents; D004726:Endosulfan
keywords: Amphibians; Behaviour; Endosulfan; Neurotransmitters; Physiology; Toxicity