Melatonin Inhibition of Pineal Enzymes in &lt;i&gt;Coturnix &lt;/i&gt;Quail

Wright, N; Preslock, James P.

doi:10.1159/000122438

Cited by 13 publications

(5 citation statements)

References 3 publications

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“…This suggests a feedback mechanism where melatonin inhibits its own synthesis [18]. In birds, it also was shown that exogenous melatonin exert a feedback inhibition upon its synthesizing enzymes, HIOMT and AANAT [33]. The mechanism by which melatonin may affect its own synthesis in the trout pineal organ remains to be elucidated.…”

Section: Discussionmentioning

confidence: 99%

Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout

Lepage¹,

Larson

Mayer

et al. 2004

Journal of Pineal Research

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The present experiments were designed to test the hypothesis that elevated dietary levels of l-tryptophan (Trp) result in elevated plasma levels of melatonin and that this increase in plasma melatonin concentration is caused by elevated melatonin production and secretion by the gastro-intestinal-tract (GIT). Feeding juvenile rainbow trout (Oncorhynchus mykiss) Trp-supplemented feed for 7 days resulted in elevated daytime plasma levels of melatonin and reduced poststress plasma cortisol concentrations. Nighttime plasma melatonin concentrations were, however, not affected by elevated dietary Trp. Moreover, stress caused a reduction in daytime plasma levels of melatonin in fish fed Trp-supplemented feed, an effect that was counteracted by treatment with an alpha-receptor antagonist. These results clearly suggest that elevated dietary intake of Trp results in an increase in the GIT production of melatonin in rainbow trout. A suggestion that was further supported by the results from an in vitro experiment demonstrating that addition of Trp to the incubation medium stimulates melatonin production and release by incubated rainbow trout GIT. The results from this study led us to suggest a possible mechanism for melatonin in mediating the effects of elevated dietary Trp on poststress plasma cortisol concentrations and aggressive behavior in rainbow trout.

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Section: Discussionmentioning

confidence: 99%

Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout

Lepage¹,

Larson

Mayer

et al. 2004

Journal of Pineal Research

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“…(2005b) observed that melatonin levels were not different at night in O. mykiss fed tryptophan‐supplemented diets, in contrast to what happened during daytime. The authors suggested two hypothesis; either (i) intestinal melatonin production was decreased during the night or (ii) melatonin itself acted in a negative feedback mechanism on pineal hormone synthesis, the second being supported by observations in both birds (Wright & Preslock ) and fish (Yanez & Meissl ). In contrast to O. mykiss , tryptophan did not alter the hormone synthesis in the gut of the D. labrax (Herrero et al .…”

Section: Tryptophan and Melatonin Synthesismentioning

confidence: 95%

Physiological roles of tryptophan in teleosts: current knowledge and perspectives for future studies

Hoseini

Pérez‐Jiménez

Costas

et al. 2017

Reviews in Aquaculture

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Tryptophan is an essential amino acid with a huge functional versatility, in addition to its participation in protein synthesis. Because of the complexity of its metabolism, and the functional relevance of several of its metabolites, it directly or indirectly participates in a wide array of physiological pathways. This amino acid is a precursor for the synthesis of the neurotransmitter/neuromodulator serotonin (5HT), the hormone melatonin and kynurenine and related compounds such as kynurenic acid, quinolinic acid or niacin. Because of this, it has a key role in the regulation of processes ranging from the neuroendocrine to the immune system in vertebrates. In aquaculture, extensive research has been performed to optimize the levels of tryptophan in the commercial diets for many fish species. Providing adequate levels of this amino acid is critically important for fish growth but also for fish welfare, as tryptophan has been shown to modulate fish behaviour, stress responses, and antioxidant and immune systems. Currently, available data suggest a wide variation in tryptophan requirements of different species ranging 0.3–1.3% of dietary protein level, but recent evidence also shows that fish tryptophan requirements can greatly vary depending on the rearing conditions of the fish. We also review here the participation of tryptophan and related metabolites in different physiological functions that are crucial for fish welfare. The review covers the involvement of tryptophan in 5HT‐ and melatonin‐mediated functions, along with its participation in the regulation of the immune system and its role as an antioxidant and antitoxic agent in fish.

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“…Several lines of evidence point to a local, intrapineal, role of melatonin. The pineal gland has a high capacity to take up melatonin from the bloodstream (22), and melatonin treatments alter several pineal morphological and biochemical parameters, including the number of dense-cored or granulated vesicles (23,24), thyroxine uptake (25), microtubular protein content (26), enzyme activity in melatonin pathway (26)(27)(28) and noradrenaline (NA) release and uptake (29). It was also early noted that melatonin injections alter 5-HT levels and block the rhythm in 5-HT content of the rat and ferret pineal gland (30,31).…”

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confidence: 99%

Evidence for a Regulatory Role of Melatonin on Serotonin Release and Uptake in the Pineal Gland

Míguez¹,

Simonneaux²,

Pévet³

1995

J Neuroendocrinology

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Melatonin has been proposed to exert some regulatory actions within the pineal gland itself. The present study examined the effect of melatonin on the release of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) from rat pineal glands by using an in vitro perifusion system. Melatonin induced a concentration-dependent stimulatory effect on 5-HT secretion from 10(-6) M to 10(-3) M. Maximal effects were obtained with melatonin 10(-3) M and concentrations lower than 10(-6) M were without effect. The secretion of 5-HIAA was inhibited by melatonin 10(-3) and 10(-4) M, but it was increased when pineals were incubated with 10(-5) and 10(-6) M of melatonin. The indoleamine secretion was also studied on peripherally denervated rat pineal glands. Basal output of 5-HT from these glands was increased when compared with those from control rats. In contrast, the secretion of 5-HIAA was strongly reduced after removal of the sympathetic input to the pineal gland. Melatonin 10(-3) M failed to stimulate 5-HT release from denervated pineal glands, although it inhibited 5-HIAA secretion. In contrast, melatonin 10(-5) M enhanced 5-HT release without altering 5-HIAA output. Fluoxetine, a 5-HT uptake inhibitor, produced similar effects than mM concentrations of melatonin on the indoleamine secretion from control pineal glands, but it had no effect on glands taken from peripherally denervated rats. These data suggest that mM concentrations of the pineal hormone are able to stimulate 5-HT release from the pinealocyte, while mM concentrations of melatonin increase extracellular 5-HT by inhibiting its reuptake in the adrenergic nerve endings. These findings are discussed in relation to the possible role of melatonin regulating the intra- and extracellular availability of 5-HT in the pineal gland and its significance as an autocrine factor.

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Melatonin Inhibition of Pineal Enzymes in <i>Coturnix </i>Quail

Cited by 13 publications

References 3 publications

Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout

Tryptophan affects both gastrointestinal melatonin production and interrenal activity in stressed and nonstressed rainbow trout

Physiological roles of tryptophan in teleosts: current knowledge and perspectives for future studies

Evidence for a Regulatory Role of Melatonin on Serotonin Release and Uptake in the Pineal Gland

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