Acute effects of L-tryptophan on tryptophan hydroxylation rate in brain regions (hypothalamus and medulla) of rainbow trout (Oncorhynchus mykiss)
✍ Scribed by Aldegunde, M.; Soengas, J.L.; Rozas, G.
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 89 KB
- Volume
- 286
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Levels of 5-hydroxytryptophan (5-HTP) in brain regions (hypopthalamus and medulla) of rainbow trout were analysed by HPLC-EC 0, 10, 30, and 40 min after intraperitoneal administration of different doses of L-tryptophan (Trp) (0, 12.5, and 25 mg • kg -1 body weight) in fish treated with 3-hydroxybenzylhydrazine (NSD1015; 75 mg • kg -1 ). The results show that, in control fish, 5-HTP levels in hypothalamus (58.03 ± 6.36 pg • mg -1 brain tissue) were significantly higher than those observed in medulla (28.04 ± 4.32 pg • mg -1 brain tissue). Basal tryptophan hydroxylation rates (after 0 mg • kg -1 Trp administration) were 0.42 ± 0.07 pg 5-HTP • mg -1 • min -1 , and 0.63 ± 0.24 pg 5HTP • mg -1 • min -1 , for hypothalamus and medulla respectively. On the other hand, the results demonstrate that L-tryptophan administration induced significant increases in the rate of tryptophan hydroxylation, both in hypothalamus and medulla. These findings indicate that, in a way similar to that observed in mammals, brain tryptophan hydroxylase is unsaturated by its substrate (tryptophan) under normal physiological conditions.