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Analysis of extracellular levels of serotonin in rat amygdala after oral administration of large amounts of tryptophan
Author(s) -
Yoshizawa Fumiaki,
Honda Manami,
Sugahara Kunio
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1013.26
Subject(s) - microdialysis , serotonin , amygdala , 5 ht receptor , tryptophan , medicine , endocrinology , chemistry , oral administration , neurotransmitter , extracellular , metabolite , pharmacology , central nervous system , receptor , biochemistry , amino acid
Serotonin (5HT) is an important neurotransmitter known to affect many behaviors. The synthesis of 5HT in the brain is dependent on the availability of tryptophan (Trp) from plasma. Therefore, oral administration of Trp affects 5HT synthesis in the brain. We focused on the amygdala, a brain structure central in the generation of both normal and pathological emotional behavior. The aim of this work was to investigate the effects of oral administration of large amounts of Trp on the extracellular levels of 5HT and its metabolite 5‐hydroxyindoleaceticacid (5HIAA) in the amygdala. The overnight fasted rats were administered Trp at concentrations ranging from 18 to 144 mg/100g BW by oral gavage. The lowest concentration of Trp employed is equivalent to that consumed in a 24‐h period by rats. Extracellular levels of 5HT and 5HIAA in rat amygdala were measured with in vivo microdialysis technique. During the observation period, no changes were observed in the levels of 5HT in all treatment groups. In contrast, the levels of 5HIAA started to increase from the basal level at one hour after oral administration of Trp, irrespective of the doses of Trp. The maximum levels of 5HIAA were almost the same among all Trp administered groups, but the higher doses of Trp had a more prolonged effect on the levels of 5HIAA. These results suggested that oral administration of large amounts of Trp induced an increase in neuronal activity in amygdala.