Glucocorticoid receptor immunoreactivity in neurons and pituitary cells implicated in reproductive functions in rainbow trout: A double immunohistochemical study

In order to identify the nature of the glucocorticoid receptor (GR)-express ing neurons and pituitary cells that potentially mediate the negative effec ts of stress on reproductive performance, double immunohistochemical staini ngs were performed in the brain and pituitary of the rainbow trout (Oncorhy nchus mykiss). To avoid possible cross-reactions during the double staining studies, combinations of primary antibodies raised in different species we re used, and we report here the generation of an antibody raised in guinea pig against the rainbow trout glucocorticoid receptor (rtGR). The results o btained in vitellogenic females showed that GnRH-positive neurons in the ca udal telencephalon/anterior preoptic region consistently exhibited rtGR imm unoreactivity. Similarly, in the anterior ventral preoptic region, a group of tyrosine hydroxylase-positive neurons, known for inhibiting gonadotropin (GTH)-2 secretion during vitellogenesis, was consistently shown to strongl y express CR. Finally, we show that a large majority of the GTH-1 (FSH-like ) and GTH-2 (LH-like) cells of the pituitary exhibit rtGR immunoreactivity. These results indicate that cortisol may affect the neuroendocrine control of the reproductive process of the rainbow trout at multiple sites.