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 status on sex hormone levels have also been reported in laboratory and wild-spawning trout, but GnRH expression was not monitored in this latter study. Although further studies will be required to dissect the molecular mechanisms potentially implicating GR in sGnRH expression in fish, it is likely that such interactions have been conserved throughout the vertebrate lineage, indicating that they are functionally important. This alone could explain some of the negative effects of stress and/or cortisol on the reproductive performance of salmonids. Our results also show that the large GnRH-immunoreactive neurons of the midbrain that express chicken GnRH-II do not express rtGR, further indicating that these cells represent another set of GnRH neurons whose functions remain to be established. Cheap Diskus Advair
A second potential cortisol target evidenced in this study concerns the TH neurons of the nucleus preopticus pars anteroventralis. There is strong evidence that these neurons are the source of the dopamine that inhibits GTH-2 secretion in both goldfish and rainbow trout. First, electrolytic lesions of this particular area in goldfish cause a large increase in GTH-2 plasma level and ovulation in female goldfish associated with the disappearance of the TH-positive fibers in the anterior lobe of the pituitary.