Evaluation of 5-Hydroxytryptophan Administration as a Test of Pineal Function in Humans

Cavallo, Anita; Richards, Gail E.; Meyer, Walter J.; Waldrop, Ron D.

doi:10.1159/000180790

Cited by 10 publications

(6 citation statements)

References 13 publications

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“…Hourly blood samples were collected continuously from a pe ripheral vein, using a constant withdrawal technique [28,29]. litis procedure enables the determination of integrated hormonal con centrations over the sampling period, which in this study was I h for each sample.…”

Section: Blood Samplingmentioning

confidence: 99%

“…Preliminary results, however, demonstrated that daytime melatonin concentrations were uniformly low, often below the limit of de tection for the assay when I-ml plasma samples were used [29,34]. Therefore, the protocol was simplified to collect blood samples only during a 14-hour overnight period, from 18.00 to 08.00 h. Figure 1 shows the 24-hour melatonin profile in 4 children.…”

Section: Blood Samplingmentioning

confidence: 99%

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Plasma Melatonin Rhythm in Normal Puberty: Interactions of Age and Pubertal Stages

Cavallo

1992

Neuroendocrinology

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Studies on the relation between the pineal and human puberty have yielded conflicting results, partly due to methodologic issues, such as failure to consider the characteristic secretory rhythm of melatonin, or exclusion of normal subjects. Melatonin nocturnal rhythm was assessed in 62 normal subjects (ages 5–17 years), in whom hourly blood samples were collected by constant withdrawal from 18.00 to 08.00 h. Melatonin peak and mean integrated nocturnal concentrations were highly correlated (r = 0.90, p < 0.05) and data are shown for melatonin peak. Tanner criteria were applied for pubertal stages. Mean melatonin peak was 153.6 ± 72.6 pg/ml for stage 1, 141.0 ± 26.2 pg/ml for stage 2, and 116.6 ± 43.6 pg/ml for stages 3–5. There was a significant linear trend for decreasing melatonin peak with puberty. The subjects were also grouped into discrete age groups (5–6.99 years through 15–17 years); a significant linear trend was present for decreasing melatonin peak with age. The correlation between melatonin peak and age for all cases was r = –0.29, p < 0.05. Analysis of covariance for melatonin peak among the pubertal groups showed no relation of melatonin and puberty when age was covaried. The time of peak was not significantly different among the pubertal groups or the age groups, despite a significant linear trend for later bedtime with age. The duration of the nocturnal surge was not significantly different among the pubertal groups. The data suggest that an overlapping effect of age may mask an interaction between the pineal and normal human puberty.

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Section: Blood Samplingmentioning

confidence: 99%

Section: Blood Samplingmentioning

confidence: 99%

Plasma Melatonin Rhythm in Normal Puberty: Interactions of Age and Pubertal Stages

Cavallo

1992

Neuroendocrinology

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“…These results provided the suggestion of the employment of this model as the base of clinical tests to investigate the pineal function. However, attempts in this sense in human beings have not been successful (Cavallo et al, 1987). It should be emphasized that in this study the authors used the oral route and lower doses of L-HTP (5-12 mg.kg -1 ).…”

Section: Resultsmentioning

confidence: 95%

“…TPO is considered the rate-limiting enzyme of the serotonin synthesis in serotoninergic neurons (Tyce, 1990;Boadle-Biber, 1993). Administration of serotonin precursors (and thus leading to melatonin synthesis) has given rise to controversial results (Namboodiri et al, 1983;Sugden et al, 1985;Cavallo et al, 1987;Reiter et al, 1990;McIntyre and Oxenkrug, 1991;Nathan et al, 1998;Steardo et al, 2000;Huether et al, 1993). However, such a model has not been employed in birds to evaluate the effect of brain serotonin precursors on melatonin synthesis.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2007

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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 , 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 L-HTP 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.Keywords: melatonin, pineal, l-5-hydroxy-tryptophan, Coturnix japonica. Níveis plasmáticos noturnos de melatonina em codornas (Coturnix japonica) injetadas com l-5-hidroxi-triptofano ResumoEste trabalho objetivou demonstrar a influência da administração sistêmica de l-5-hidroxi-triptofano (L-HTP) sobre os níveis plasmáticos de melatonina durante o período noturno em codornas. Ao longo do período claro, os níveis plasmáticos de melatonina não diferiram significativamente, oscilando entre 110,2 ± 15,8 pg.mL -1 e 157,4 ± 34,8 pg.mL , respectivamente, às 20 e 24 horas, P < 0,05). Os resultados obtidos mostraram que a administração de L-HTP reduziu a liberação noturna de melatonina, possivelmente por suscitar um aumento da síntese e liberação sináptica de serotonina na pineal. Portanto, a transmissão serotoninérgica da rafe para a pineal constituiria um mecanismo de modulação da síntese e/ou liberação de melatonina em codornas.Palavras-chave: melatonina, pineal, l-5-hidroxi-triptofano, Coturnix japonica.

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“…In another study, subjects ingested 6 grams of tryptophan and plasma melatonin levels increased approximately 12 pg/ml after five hours (Christofides, et al, 2006). In the case of oral administration of 600 -800 mg 5-hydroxy tryptophan, plasma melatonin levels did not increase above the detection limit of 15.6 pg/ml (Cavallo, et al, 1987). It is thus unlikely that melatonin precursors are responsible for the reported melatonin increases.…”

Section: What Are the Possible Explanations For The Detection Of Melamentioning

confidence: 93%

Are the proposed benefits of melatonin-rich foods too hard to swallow?

Kennaway

2016

Critical Reviews in Food Science and Nutrition

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Melatonin has been proposed as a potent anti-oxidant, and its presence in many plants and foods has been suggested to be beneficial for health. Indeed, the concentrations of melatonin in blood and the melatonin metabolite 6 sulphatoxymelatonin in urine have been found to increase significantly after ingestion of melatonin-rich foods. In this review, the studies have been critically evaluated in light of the reported plant melatonin concentrations and our knowledge of pharmacokinetics of orally administered pure melatonin. In the case of studies involving measurement of plasma melatonin following ingestion of beer or fruits, the reported increase in melatonin is not consistent with the amount of melatonin ingested. Similarly, the amount of melatonin metabolite excreted following ingestion of melatonin-rich foods greatly exceeded the amount of melatonin ingested. It is concluded that studies reporting the appearance of melatonin in blood and its metabolites in urine following ingestion of melatonin-rich foods are flawed. While there may be health benefits for certain foods, it is difficult to accept that these are due to their low melatonin content.

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Evaluation of 5-Hydroxytryptophan Administration as a Test of Pineal Function in Humans

Cited by 10 publications

References 13 publications

Plasma Melatonin Rhythm in Normal Puberty: Interactions of Age and Pubertal Stages

Plasma Melatonin Rhythm in Normal Puberty: Interactions of Age and Pubertal Stages

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

Are the proposed benefits of melatonin-rich foods too hard to swallow?

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