Brain serotonin and the control of food intake in rainbow trout (Oncorhynchus mykiss): effects of changes in plasma glucose levels.
The levels of 5-hydroxytryptamine and its main metabolite 5-hydroxyindoleacetic acid were assessed in two brain regions, hypothalamus and telencephalon, of rainbow trout (Oncorhynchus mykiss) submitted to increases or decreases in plasma glucose levels through different experimental approaches. Thus, intraperitoneal glucose treatment (500 mg kg(-1)) increased 5-hydroxytryptamine telencephalic levels. Long-term food deprivation up to 3 weeks significantly increased hypothalamic (2 weeks and 3 weeks) and telencephalic (1 week, 2 weeks, and 3 weeks) levels of 5-hydroxyindoleacetic acid, whereas the ratio 5-hydroxyindoleacetic acid/5-hydroxytryptamine significantly increased throughout the food-deprivation period assessed. Intraperitoneal treatment with bovine insulin (4 mg kg(-1)) decreased the 5-hydroxyindoleacetic acid/5-hydroxytryptamine ratio in hypothalamus after 1 h. Intraperitoneal administration of fenfluramine (3 mg kg(-1)) caused a depression in food intake coincident with a significant decrease of the hypothalamic 5-hydroxyindoleacetic acid/5-hydroxytryptamine ratio. These data are discussed in the context of the involvement of serotonergic system in the control of food intake in rainbow trout.
Laboratorio de Fisioloxía Animal (Dpto. de Fisioloxía), Facultade de Bioloxía, Universidade de Santiago de Compostela, Spain.
C
C
Ruibal
J L
JL
Soengas
M
M
Aldegunde
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D005277:Fenfluramine / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D018490:Serotonin Agents / Q000494:pharmacology; D013687:Telencephalon / Q000378:metabolism
D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D018490:Serotonin Agents; D005277:Fenfluramine; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D005947:Glucose