Involvement of Estradiol in a Catecholamine Inhibitory Tone of Gonadotropin Release in the Rainbow Trout (Oncorhynchus mykiss)

Linard, Boris; Bennani, Sanae; Saligaut, Christian

doi:10.1006/gcen.1995.1101

Cited by 79 publications

(45 citation statements)

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“…The activity of brain aromatase changes significantly along the reproductive cycle, being associated with changes in the metabolism of brain catecholamines. It was shown that the application of estradiol to fish evoked an increased activity of pituitary neurones producing dopamine (Linard et al, 1995(Linard et al, , 1996Saligaut et al, 1998). Moreover, there is immunohistochemical evidence that the dopamine containing neurons reaching the pituitary gland possess estrogenic receptors (Linard et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

“…This arouses serious problems for carp farmers and commercial hatcheries in which the products containing antidopaminergic drugs were used for years. It was recently discovered that the high level of dopamine, affecting LH secretion, is determined by the high levels of circulating estradiol (Linard et al, 1995;Saligaut et al, 1998). In the last stages of ovarian maturity, just before ovulation, the drop of dopamine production follows a rapid drop of estradiol levels.…”

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confidence: 99%

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LH secretion and 17ββ-estradiol concentration in the blood plasma and hypothalamus of goldfish (Carassius auratus gibelio B.) and common carp (Cyprinus carpio L.) treated with fadrozole (aromatase inhibitor) and GnRH analogues

Mikołajczyk¹,

Sokolowska-Mikolajczyk²,

Chyb³

et al. 2007

CZECH J ANIM SCI

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Fadrozole -a non-steroidal aromatase inhibitor was applied to common carp and goldfish to examine its ability to potentiate the stimulatory action of GnRH analogues on LH secretion in vivo. The goal of the project was to find a substitute for antidopaminergic drugs used with GnRH analogues in fisheries practice to stimulate ovulation in fish bred in captivity. The first trials on goldfish showed a moderate ability of fadrozole to potentiate salmon GnRH analogue stimulation, weaker than that obtained with pimozide (dopamine antagonist). No ovulation in fadrozole-treated fish was observed. Several experiments performed in two consecutive reproductive seasons (different treatment regimes and doses of fadrozole) neither improved nor confirmed the results obtained in the first year. The analysis of 17β-estradiol levels in the blood plasma and in hypothalami showed no changes in the concentration of this steroid in fadrozole-treated fish in comparison with the controls. This shows that fadrozole is not able to replace the antidopaminergic drugs used in fisheries practice and cannot be considered as a potential ovulation inducer in cyprinids.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

LH secretion and 17ββ-estradiol concentration in the blood plasma and hypothalamus of goldfish (Carassius auratus gibelio B.) and common carp (Cyprinus carpio L.) treated with fadrozole (aromatase inhibitor) and GnRH analogues

Mikołajczyk¹,

Sokolowska-Mikolajczyk²,

Chyb³

et al. 2007

CZECH J ANIM SCI

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“…It has been suggested that the dopaminergic neurons of the NPOav are involved in the négative feedback effect of estradiol on GTH-II release . This hypothesis is supported by the fact that in trout an estradiol-dependent dopaminergic inhibitory tone on GTH-II sécrétion originates from the NPOav and that thèse dopaminergic neurons express the rtER (LINARD et al, 1995 ;LINARD et al, 1997). Although the molecular targets of estradiol in thèse cells remain to be demonstrated, it is likely that estradiol via its receptor modulâtes the activity of thèse neurons to inhibit GTH-II sécrétion.…”

Section: Discussionmentioning

confidence: 95%

Distribution of glucocorticoid receptors in the brain of rainbow trout (Oncorhynchus mykiss): possible relationships with the neuroendocrine systems controlling reproduction

Teitsma

Anglade

Bailhache

et al. 1998

Bull. Fr. Pêche Piscic.

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The distribution of the glucocorticoid receptor (GR) within the forebrain of rainbow trout has been studied by means of in situ hybridization (ISH) and immunohistochemistry (ICC) using probes and antibodies directed against the AB-domain of the rainbow trout GR (rtGR).Both rtGR mRNA and protein exhibited the same pattern of distribution. A strong labelling was observed in ail subdivisions of the preoptic nucleus, in the thalamic région and in the mediobasal hypothalamus (nucleus recessus lateralis, nucleus lateralis tuberis). It was notably found that ail magnocellular neurons of the nucleus preopticus pars magnocellularis (NPOmc) were positive with both ISH and ICC. Furthermore, numerous cells of the anterior lobe of the pituitary were positively stained. Double staining studies allowed to identify part of the rtGR expressing cells. At the telencephalic level, it was found that GnRH neurons frequently express rtGR in vitellogenic females. Virtually ail tyrosine hydroxylase (TH) cells in the anteroventral part of the preoptic nucleus (NPOav) were rtGR-positive. In this same area, a colocalization between rainbow trout estradiol receptor (rtER) and TH has already been documented, indirectly demonstrating that rtER and rtGR are colocalized. The same holds true for the GTH-II cells of the anterior pituitary which express both types of receptors.Thèse results provide information on the potential sites of cortisol action on the reproductive axis directly at the pituitary level or indirectly on neuroendocrine Systems controlling GTH-II sécrétion, possibly via GR-ER interactions. DISTRIBUTION DES RÉCEPTEURS AUX GLUCOCORTICOÏDES DANS LE CERVEAU DE LA TRUITE ARC-EN-CIEL (ONCORHYNCHUS MYKISS) : RELATIONS POSSIBLES AVEC LES SYSTÈMES NEUROENDOCRINIENSCONTRÔLANT LA REPRODUCTION. RÉSUMÉLa distribution du récepteur aux glucocorticoïdes (GR) dans le cerveau de la truite arc-en-ciel a été étudiée par les techniques d'hybridation in situ (HIS) et d'immunocytochimie (ICC) utilisant des sondes et des anticorps dirigés contre le domaine AB du GR de truite (rtGR).Les sites d'expression de l'ARNm et de la protéine rtGR sont très similaires. Les deux méthodes ont permis de mettre en évidence un marquage au niveau des différentes sousdivisions du noyau préoptique (NPO), en particulier au niveau des neurones Article available at

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“…This study and our previous immunohistochemical observations [29]that both GABA- and GnRH-immunoreactive fibers are found close to each other in the neurohypophyseal digitations, adjacent to the gonadotropic cells, suggest that a morphofunctional support exists for such GnRH-GABA interactions in the proximal pars distalis of the rainbow trout, although it remains to be demonstrated. Alternatively, as GTH-2 release in rainbow trout requires the removal of an estrogen-dependent dopaminergic inhibition [37, 38, 39], it might be possible that GABA facilitates the decrease of the dopaminergic turnover, as shown in goldfish at the level of the pituitary [17]. …”

Section: Discussionmentioning

confidence: 99%

Involvement of γ-Aminobutyric Acid in the Control of GTH-1 and GTH-2 Secretion in Male and Female Rainbow Trout

et al. 1999

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The potential role of the neurotransmitter γ-aminobutyric acid (GABA) in the control of the secretion of the two pituitary fish gonadotropins (GTH-1 and GTH-2) was investigated in male and female rainbow trout (Oncorhynchus mykiss). The presence of glutamate decarboxylase-positive fibers in the neurohypophyseal digitations adjacent to the gonadotropic cells was demonstrated by means of double immunohistochemistry, providing a morphofunctional support for potential GABA-gonadotropin interactions in both sexes. In spermiating males, in vivo treatment with GABA did not affect basal gonadotropin release, but stimulated GTH-1 release when coadministered with a gonadotropin-releasing hormone analogue (GnRHa), and potentiated GnRHa-stimulated GTH-2 release. In vitro, using dispersed pituitary cells, GABA stimulated basal GTH-1 and GTH-2 secretion, in a dose-dependent manner, and potentiated salmon GnRH effect on both hormones. In mature females, GABA induced in vivo a strong elevation of plasma GTH-2 levels after 2– 6 h of injection, but had no effect in vitro. GABA treatment in vivo was also stimulatory in recrudescent females, slightly increasing plasma GTH-2 levels in both saline- and GnRHa-treated fish (GnRHa alone has no effect at this stage). Immature fish were unresponsive to GABA/GnRHa treatments but, after steroid implantation [testosterone (T) or estradiol] for 13 days, injection of GABA stimulated GTH-2 release in vivo (also GTH-1 slightly in T-implanted fish). In conclusion, GABA has an overall stimulatory action on GTH-1 and GTH-2 secretion in rainbow trout, which depends on the sex and the reproductive stage of the fish. The stimulatory action of GABA might be exerted, at least in part, directly onto the gonadotropes, as it stimulates basal and GnRH-induced GTH-1 and GTH-2 secretion from dispersed pituitary cells.

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Involvement of Estradiol in a Catecholamine Inhibitory Tone of Gonadotropin Release in the Rainbow Trout (Oncorhynchus mykiss)

Cited by 79 publications

References 0 publications

LH secretion and 17ββ-estradiol concentration in the blood plasma and hypothalamus of goldfish (Carassius auratus gibelio B.) and common carp (Cyprinus carpio L.) treated with fadrozole (aromatase inhibitor) and GnRH analogues

LH secretion and 17ββ-estradiol concentration in the blood plasma and hypothalamus of goldfish (Carassius auratus gibelio B.) and common carp (Cyprinus carpio L.) treated with fadrozole (aromatase inhibitor) and GnRH analogues

Distribution of glucocorticoid receptors in the brain of rainbow trout (Oncorhynchus mykiss): possible relationships with the neuroendocrine systems controlling reproduction

Involvement of γ-Aminobutyric Acid in the Control of GTH-1 and GTH-2 Secretion in Male and Female Rainbow Trout

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