Central nervous system actions of growth hormone on brain monoamine levels and behavior of juvenile rainbow trout.
Growth hormone (GH) has been demonstrated to alter the behavior of juvenile salmonids. However, the mechanisms behind this action are not yet understood. In mammals and birds, peripheral GH treatment has been shown to affect monoaminergic activity in the central nervous system, which may be a mechanism whereby GH alters behavior. To investigate if GH may influence behavior directly at the central nervous system, juvenile rainbow trout were injected with GH into the third ventricle of the brain, whereupon physical activity and food intake were observed during 2 h. Thereafter, brains were sampled and the content of serotonin, dopamine, and noradrenaline and their metabolites were measured in hypothalamus, telencephalon, optic tectum, and brainstem. The GH-treated fish increased their swimming activity relative to sham-injected controls, while appetite remained unchanged, compared with sham-injected controls. Analysis of brain content of monoamines revealed that the GH treatment caused a decrease in the dopamine metabolite homovanillic acid in the hypothalamus, indicating a lowered dopaminergic activity. It is concluded that GH may alter behavior by acting directly on the central nervous system in juvenile rainbow trout. Furthermore, GH seems to alter the dopaminergic activity in the hypothalamus. Whether this is a mechanism whereby GH affects swimming activity remains to be clarified.
Jönsson
Elisabeth
E
Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, Göteborg University, Box 463, Sweden. elisabeth.jonsson@zool.gu.se
Johansson
Viktoria
V
Björnsson
Björn Thrandur
BT
Winberg
Svante
S
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D015306:Biogenic Monoamines / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects*; D002490:Central Nervous System / Q000187:drug effects*; D004298:Dopamine / Q000378:metabolism; D004435:Eating / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007276:Injections, Intraventricular; D009043:Motor Activity / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D013550:Swimming / Q000523:psychology
D015306:Biogenic Monoamines; D012701:Serotonin; D013006:Growth Hormone; D004298:Dopamine; D009638:Norepinephrine