Glucocorticoid Receptor Immunoreactivity: DISCUSSION(7)

In the liver of rainbow trout, the estrogen receptor gene is positively regulated by estradiol, and it is known that both basal and estradiol-stimulated expression of the estrogen receptor in the liver are inhibited by dexamethasone—an effect that is likely to take place at the transcriptional level (unpublished results). Therefore, it is possible that glucocorticoids…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(6)

Although it has been shown in vivo that glucocorticoids inhibit both spontaneous and GnRH-stimulated LH secretion, the opposite results were obtained in vitro. Glucocorticoids were also shown to inhibit GnRH-induced LHa and LHp mRNA transcription, but not that of FSHp. At the present stage, the effects of glucocorticoid on GTH synthesis and release in fish…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(5)

In mammals, extensive studies have documented the presence of GR immunore-activity in catecholamine^c neurons, and it is well known that glucocorticoids and/or dexamethasone increase the steady-state levels of TH mRNA under various stress conditions in vivo and in vitro. However, the precise sites for GR binding on the TH promoter remain unidentified, raising the possibility…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(4)

Second, retrograde tracing studies in goldfish, rainbow trout, and Atlantic salmon have clearly indicated that neurons in this area are hypophysiotropic. Furthermore, in Atlantic salmon, retrograde studies combined with TH immunohistochemistry have unambiguously demonstrated that these TH neurons are hypophysiotropia. In goldfish, rainbow trout, and Atlantic salmon, it is also known that these TH-positive neurons…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(3)

A recent study in the African cichlid (Haplochromis burtoni) has shown a relationship between social status, cortisol levels, and size of GnRH perikarya in the preoptic area, indicating that GnRH expression might be one of the factors involved in the suppression of reproductive maturation in subordinate versus dominant fish in territorial species. Effects of dominance…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(2)

With respect to GnRH neurons, our results clearly show that in these vitellogenic females, a large majority (at least 70%) of the sGnRH-producing neurons in the ventro-caudal telencephalon and anterior preoptic region express rtGR. Results in rats have already shown that, in the homologous regions, medial septum-lateral band of Broca and preoptic area, a subset…

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Glucocorticoid Receptor Immunoreactivity: DISCUSSION(1)

This study provides further information on the central expression of GR in a teleost species and demonstrates that the main neuronal populations involved in the regulation of GTH-2 secretion are likely to be regulated by cortisol in rainbow trout. In addition, we show that both GTH-1 and GTH-2 cells strongly express rtGR. Although the precise…

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