title: Disturbances to neurotransmitter levels and their metabolic enzyme activity in a freshwater planarian exposed to cadmium.
abstract: Using specific neurobehaviors as endpoints, previous studies suggested that planarian neurotransmission systems could be targets of Cd neurotoxicity. However, direct evidence for disturbed neurotransmission systems by Cd in treated planarians is still lacking. In planarians, dopamine (DA) and serotonin (5-HT) play critical roles in neuromuscular function, but little is known about their metabolic degradation. Therefore, in this study, we attempted to determine the appearances of DA, 5-HT, and their metabolic products in the freshwater planarian Dugesia japonica, characterize the activity of enzymes involved in their metabolism, and investigate the effects of Cd on planarian 5-HTergic and DAergic neurotransmission systems. Only DA, 5-HT, and 5-hydroxyindole-3-acetic acid (5-HIAA) were found in planarian tissues. Further enzymatic study revealed the activity of planarian monoamine oxidase (MAO) but not catechol-O-methyl transferase (COMT). These findings suggest that planarian MAO catalyzes the metabolism of 5-HT into 5-HIAA. However, DA metabolites from the MAO-involved metabolic pathway were not found, which might be due to a lack of COMT activity. Finally, in Cd-treated planarians, tissue levels of 5-HT and DA were decreased and MAO activity altered, suggesting that planarian neurotransmission systems are disturbed following Cd treatment.
authors: Environmental Toxicology Laboratory, Department of Geography, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 106, Taiwan. Electronic address: rb5_wu@yahoo.com.tw.
authors: Jui-Pin
authors: JP
authors: Wu
authors: Environmental Toxicology Laboratory, Department of Geography, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 106, Taiwan. Electronic address: meihuili@ntu.edu.tw.
authors: Mei-Hui
authors: MH
authors: Li
authors: Department of Chemistry, Fu Jen Catholic University, 510, Zhongzheng Road, Xinzhuang District, New Taipei City 24205, Taiwan. Electronic address: george7739@hotmail.com.
authors: Jhih-Sheng
authors: JS
authors: Chen
authors: Department of Chemistry, Fu Jen Catholic University, 510, Zhongzheng Road, Xinzhuang District, New Taipei City 24205, Taiwan. Electronic address: csy12190115@hotmail.com.
authors: Szu-Yao
authors: SY
authors: Chung
authors: Department of Chemistry, Fu Jen Catholic University, 510, Zhongzheng Road, Xinzhuang District, New Taipei City 24205, Taiwan. Electronic address: 076308@mail.fju.edu.tw.
authors: Hui-Ling
authors: HL
authors: Lee
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002394:Catechol O-Methyltransferase / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D008995:Monoamine Oxidase / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D010932:Planarians / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism
chemical_list: D018377:Neurotransmitter Agents; D002104:Cadmium; D012701:Serotonin; D008995:Monoamine Oxidase; D002394:Catechol O-Methyltransferase; D004298:Dopamine
keywords: 5-Hydroxyindole-3-acetic acid (5-HIAA); Dugesia japonica; Invertebrates; Metal; Neurotoxicity