Effects of melatonin on dopamine metabolism in the hypothalamus and the pituitary of the rainbow trout, Oncorhynchus mykiss

Hernandez-Rauda, Roberto; Míguez, Jesús M.; Ruibal, C.; Aldegunde, Manuel

doi:10.1002/1097-010x(20001101)287:6<440::aid-jez5>3.3.co;2-j

Cited by 3 publications

(4 citation statements)

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“…However, an earlier study in the same species reported that high melatonin doses did not affect DA turnover in the hypothalamus (106). In rainbow trout, melatonin inferred a decrease in the hypothalamic‐pituitary DA turnover (107), a supposed step by which melatonin modulated LH secretion, as indicated in a previous study (108). In carp, Cyprinus carpio , a similar suggestion was proposed as melatonin was shown to inhibit DA release in hypothalamus both in vivo and in vitro (109, 110).…”

Section: Discussionmentioning

confidence: 80%

Melatonin Activates Brain Dopaminergic Systems in the Eel with an Inhibitory Impact on Reproductive Function

Sébert

Legros

Weltzien

et al. 2008

J Neuroendocrinology

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In the eel, a deficit in gonadotrophin-releasing hormone (GnRH) and a strong dopaminergic (DA) inhibition are responsible for the blockade of gonad development if silver eels are prevented from their reproductive migration. Environmental factors that eels encounter during their oceanic reproductive migration are thought to play an important role in the stimulation of eel pubertal development. We investigated the potential role of melatonin, a known mediator of the effects of external factors on reproductive function in vertebrates. We demonstrated that a long-term melatonin treatment increased brain tyrosine hydroxylase (TH, the rate limiting enzyme of DA synthesis) mRNA expression in a region-dependent way. Melatonin stimulated the dopaminergic system of the preoptic area, which is involved in the inhibitory control of gonadotrophin [luteinising hormone (LH) and follicle-stimulating hormone (FSH)] synthesis and release. Moreover, we showed that the increased TH expression appeared to be consistent with melatonin binding site distribution as shown by 2[(125)I]-melatonin labelling studies. On the other hand, melatonin had no effects on the two eel native forms of GnRH (mGnRH and cGnRH-II) mRNA expression. Concerning the pituitary-gonad axis, we showed that melatonin treatment decreased both gonadotrophin beta-subunit (LHbeta, FSHbeta) mRNA expression and reduced sexual steroid (11-ketotestosterone, oestradiol) plasma levels. This indicates that melatonin treatment had a negative effect on eel reproductive function. To our knowledge, the results of the present study provide the first evidence that melatonin enhances TH expression in specific brain regions in a non-mammalian species. By this mechanism melatonin could represent one pathway by which environmental factors could modulate reproductive function in the eel.

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Section: Discussionmentioning

confidence: 80%

Melatonin Activates Brain Dopaminergic Systems in the Eel with an Inhibitory Impact on Reproductive Function

Sébert

Legros

Weltzien

et al. 2008

J Neuroendocrinology

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“…Keeping in mind that feeding is stimulated by NE and reduced by DA in goldfish [30,51], melatonin could probably reduce feeding and body weight by inhibiting noradrenergic activity and/or stimulating dopaminergic activity in fish hypothalamus. Herna´ndez-Rauda et al [52] found that a single melatonin injection reduces dopaminergic metabolism in hypothalamus of the rainbow trout, but feeding behavior was not evaluated. Nevertheless, it cannot be discounted that the reduction of DOPAC clearance may also contribute to the DOPAC increase found in the present study.…”

Section: Discussionmentioning

confidence: 99%

“…Hernández‐Rauda et al. [52] found that a single melatonin injection reduces dopaminergic metabolism in hypothalamus of the rainbow trout, but feeding behavior was not evaluated. Nevertheless, it cannot be discounted that the reduction of DOPAC clearance may also contribute to the DOPAC increase found in the present study.…”

Section: Discussionmentioning

confidence: 99%

Melatonin reduces body weight in goldfish (Carassius auratus): effects on metabolic resources and some feeding regulators

Pedro

Martínez‐Álvarez

Delgado

2008

Journal of Pineal Research

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The objective of the present study was to analyze the effects of chronic melatonin (10 microg/g body weight) on body weight and the main energetic reserves, particularly hepatic and muscle content of proteins, lipids and glycogen in goldfish. In addition, we studied plasma leptin and ghrelin, and hypothalamic content of neuropeptide Y (NPY) and monoamines after chronic melatonin treatment in order to elucidate a possible interplay between melatonin and these feeding regulators on the body weight regulation in this species. Body weight gain and specific growth rate were reduced (74% and 76%, respectively) after chronic (10 days) intraperitoneal (i.p.) treatment with melatonin. The carbohydrate and lipid metabolism was regulated by melatonin in goldfish, because this indoleamine reduced muscle glycogen stores and increased lipid mobilization. A suppressive trend, but not statistically significant, in circulating ghrelin was observed after chronic treatment with melatonin. Chronic melatonin administration significantly reduced noradrenergic metabolism and increased dihydroxiphenylacetic acid content in the hypothalamus, without significant modifications in the serotoninergic system. Thus, it could be suggested that melatonin may mediate its action on energy balance in fish, at least in part, via interactions with hypothalamic catecholaminergic system. Plasma leptin and hypothalamic NPY remained unaltered after melatonin treatment, suggesting that these feeding regulators may not be involved in the effects of melatonin on energy homeostasis in fish.

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“…An earlier study on the same species, however, reported that high melatonin doses did not affect hypothalamic DA turnover (Senthilkumaran & Joy, 1995). In O. mykiss , melatonin induced a fall in the hypothalamic‐pituitary DA turnover (Hernandez‐Rauda et al , 2000). As proposed in a previous study, by this negative effect, melatonin would modulate LH secretion (Saligaut et al , 1998).…”

Section: Regulation Of Dopaminergic Inhibitionmentioning

confidence: 99%

Neuroendocrine control by dopamine of teleost reproduction

Dufour

Sébert

Weltzien

et al. 2010

Journal of Fish Biology

150

123

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While gonadotropin-releasing hormone (GnRH) is considered as the major hypothalamic factor controlling pituitary gonadotrophins in mammals and most other vertebrates, its stimulatory actions may be opposed by the potent inhibitory actions of dopamine (DA) in teleosts. This dual neuroendocrine control of reproduction by GnRH and DA has been demonstrated in various, but not all, adult teleosts, where DA participates in an inhibitory role in the neuroendocrine regulation of the last steps of gametogenesis (final oocyte maturation and ovulation in females and spermiation in males). This has major implications for inducing spawning in aquaculture. In addition, DA may also play an inhibitory role during the early steps of gametogenesis in some teleost species, and thus interact with GnRH in the control of puberty. Various neuroanatomical investigations have shown that DA neurones responsible for the inhibitory control of reproduction originate in a specific nucleus of the preoptic area (NPOav) and project directly to the region of the pituitary where gonadotrophic cells are located. Pharmacological studies showed that the inhibitory effects of DA on pituitary gonadotrophin production are mediated by DA-D2 type receptors. DA-D2 receptors have now been sequenced in several teleosts, and the coexistence of several DA-D2 subtypes has been demonstrated in a few species. Hypophysiotropic DA activity varies with development and reproductive cycle and probably is controlled by environmental cues as well as endogenous signals. Sex steroids have been shown to regulate dopaminergic systems in several teleost species, affecting both DA synthesis and DA-D2 receptor expression. This demonstrates that sex steroid feedbacks target DA hypophysiotropic system, as well as the other components of the brain-pituitary gonadotrophic axis, GnRH and gonadotrophins. Recent studies have revealed that melatonin modulates the activity of DA systems in some teleosts, making the melatonin-DA pathway a prominent relay between environmental cues and control of reproduction. The recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various internal and environmental cues. The plasticity of the DA neuroendocrine role observed in teleosts may have contributed to their large diversity of reproductive cycles.

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Effects of melatonin on dopamine metabolism in the hypothalamus and the pituitary of the rainbow trout, Oncorhynchus mykiss

Cited by 3 publications

References 0 publications

Melatonin Activates Brain Dopaminergic Systems in the Eel with an Inhibitory Impact on Reproductive Function

Melatonin Activates Brain Dopaminergic Systems in the Eel with an Inhibitory Impact on Reproductive Function

Melatonin reduces body weight in goldfish (Carassius auratus): effects on metabolic resources and some feeding regulators

Neuroendocrine control by dopamine of teleost reproduction

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