Brazilian Journal of Biology ()

Nocturnal plasma levels of melatonin in quails (Coturnix japonica) injected with l-5-hydroxy-tryptophan

  • LC. Reis,
  • AC. Almeida,
  • MC. Ribeiro,
  • PA. Polo,
  • EL. Olivares,
  • MA. Medeiros,
  • KO. Nonaka,
  • LR. Castilhos

DOI
https://doi.org/10.1590/S1519-69842007000200025
Journal volume & issue
Vol. 67, no. 2
pp. 369 – 371

Abstract

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This study aimed to demonstrate the influence of the systemic administration of l-5-hydroxy-tryptophan (L-HTP) on the plasma levels of melatonin during the dark period in quails. Throughout daylight, the plasma levels of melatonin did not differ significantly, oscillating between 110.2 ± 15.8 pg.mL-1 and 157.4 ± 34.8 pg.mL-1, from 8 to 16 hours. L-HTP (25 mg.kg-1, through the intracelomic route) administered at 18 hours lessened significantly the nocturnal increase of the plasma levels of melatonin (controls, 327.3 ± 20.1 and 315.8 ± 20.9 pg.mL-1 vs. 242.1 ± 24.8 and 217.5 ± 21 pg.mL-1, respectively, at 20 and 24 hours, P < 0.05). The results obtained showed that the administration of LHTP reduced the nocturnal melatonin release, possibly by bringing about an increase in serotonin synthesis and synaptic release in the pineal. Therefore, the serotoninergic transmission from the raphe towards the pineal would constitute a mechanism of modulation of the synthesis and melatonin release in quails.

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