title: Oral administration of melatonin counteracts several of the effects of chronic stress in rainbow trout.
abstract: To assess a possible antistress role of melatonin in fish, we orally administered melatonin to rainbow trout for 10 d and then kept the fish under normal or high stocking density conditions during the last 4 d. Food intake; biochemical parameters in plasma (cortisol, glucose, and lactate concentrations); liver (glucose and glycogen concentrations, and glycogen synthase activity); enzyme activities of amylase, lipase, and protease in foregut and midgut; and content of the hypothalamic neurotransmitters dopamine and serotonin, as well as their oxidized metabolites, 3,4-dihydroxyphenylacetic acid and 5-hydroxy-3-indoleacetic acid, were evaluated under those conditions. High stocking density conditions alone induced changes indicative of stress conditions in plasma cortisol concentrations, liver glycogenolytic potential, the activities of some digestive enzymes, and the 3,4-dihydroxyphenylacetic acid-to-dopamine and 5-hydroxy-3-indoleacetic acid-to-serotonin ratios in the hypothalamus. Melatonin treatment in nonstressed fish induced an increase in liver glycogenolytic potential, increased the activity of some digestive enzymes, and enhanced serotoninergic and dopaminergic metabolism in hypothalamus. The presence of melatonin in stressed fish resulted in a significant interaction with cortisol concentrations in plasma, glycogen content, and glycogen synthase activity in liver and dopaminergic and serotoninergic metabolism in the hypothalamus. In general, the presence of melatonin mitigated several of the effects induced by stress, supporting an antistress role for melatonin in rainbow trout.
authors.affiliation: Animal Physiology Laboratory, Department of Functional Biology and Health Sciences, Faculty of Biology, University of Vigo, E-36310 Vigo, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Conde-Sieira
authors.affiliation: I-Mar Center, University of Lagos, Puerto Montt, Casilla 557, Chile.
authors.forename: J L P
authors.initials: JL
authors.lastname: Muñoz
authors.affiliation: Animal Physiology Laboratory, Department of Functional Biology and Health Sciences, Faculty of Biology, University of Vigo, E-36310 Vigo, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: López-Patiño
authors.affiliation: Animal Physiology Laboratory, Department of Functional Biology and Health Sciences, Faculty of Biology, University of Vigo, E-36310 Vigo, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gesto
authors.affiliation: Animal Physiology Laboratory, Department of Functional Biology and Health Sciences, Faculty of Biology, University of Vigo, E-36310 Vigo, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Soengas
authors.affiliation: Animal Physiology Laboratory, Department of Functional Biology and Health Sciences, Faculty of Biology, University of Vigo, E-36310 Vigo, Spain. Electronic address: jmmiguez@uvigo.es.
authors.forename: J M
authors.initials: JM
authors.lastname: Míguez
mesh_terms: D000681:Amylases / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004435:Eating / Q000187:drug effects / Q000502:physiology; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood*; D007031:Hypothalamus / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008049:Lipase / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008550:Melatonin / Q000494:pharmacology*; D017686:Oncorhynchus mykiss / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects* / Q000502:physiology
chemical_list: D001786:Blood Glucose; D012701:Serotonin; D019344:Lactic Acid; D006003:Glycogen; D008049:Lipase; D000681:Amylases; D010447:Peptide Hydrolases; D008550:Melatonin; D004298:Dopamine; D006854:Hydrocortisone
keywords: Brain neurotransmitters; Cortisol; Food intake; Melatonin; Stress; Trout