Distribution and Expression of Glucocorticoid Receptor mRIMA in the Forebrain of the Rainbow Trout

Abstract

The expression and distribution of glucocorticoid receptor mRNA was studied in the forebrain of mature female and immature undifferentiated rainbow trout (Oncorhynchus mykiss) by means of Northern blotting and in situ hybridization. A single mRNA species of 7.5 kb was detected in mRNA polyA⁺ prepared from the anterior brain. In situ hybridization was carried out using a ³⁵S-labelled riboprobe corresponding to the A/B-domain (between nucleotides 1224 and 1763) of the recently cloned rainbow trout glucocorticoid receptor cDNA. Comparison of adjacent sections hybridized with the sense and antisense probes allowed detection of a specific signal with a similar distribution pattern in all animals studied. In the telencephalon, a specific hybridization was detected in scattered cells of the dorsal telencephalic hemisphere, but the stronger signal was consistently observed in the dorsal nucleus, and to a lesser degree in the ventral nucleus of the ventral telencephalon. Heavy hybridization staining was consistently observed in all subdivisions of the preoptic nucleus and the nucleus lateralis tuberis, which are the main hypophysiotrophic regions in fish. A weaker signal was detected in the nucleus anterioris periventricularis, nucleus suprachiasmaticus and thalamic region. The presence of a strong signal in virtually all magnocellular neurons of the nucleus preopticus, known for producing vasotocin, isotocin and corticotropin-releasing factor favors a direct function of cortisol in regulating its own secretion.

The effects of cortisol administration on social status and brain monoaminergic activity in rainbow troutOncorhynchus mykiss

“…In mammals, MRs and GRs exhibit different expression patterns in the brain and play different roles in mediating the effects of corticosteroids (Chaouloff, 2000;Korte, 2001). GRs are widely distributed in the forebrain of rainbow trout (Teitsma et al, 1997(Teitsma et al, , 1998 and the recently identified fish MR (Colombe et al, 2000;Greenwood et al, 2003;Sturm et al, 2005) also appears to be present in the brain (Greenwood et al, 2003;Sturm et al, 2005). However, the relative distributions and roles of the two corticosteroid receptors in fish brains remain to be explored.…”

Peritoneal cavity phagocytes from the teleost sea bass express a glucocorticoid receptor (cloned and sequenced) involved in genomic modulation of the in vitro chemiluminescence response to zymosan

“…Greenwood et al (2003) sequenced two distinct GR cDNA (HbGR1 and HbGR2) from tissues of Burton's mouth breeder (Haplochromis burtoni). In addition, transcripts were found in a number of tissues (Takeo et al, 1996;Teitsma et al, 1997;Uchida et al, 1998;Perry, 1997), whereas data are lacking on GR expression in Wsh leukocytes.…”

Immunohistochemical localization of glucocorticoid receptors in the forebrain of the rainbow trout (Oncorhynchus mykiss)

“…When expressed in a reticulocyte lysate system, this rainbow trout glucocorticoid receptor (rtGR) showed high affinity for glucocorticoids and virtually none for aldosterone or gonadal steroids (Ducouret et al, 1995). Northern blot analysis showed a single messenger RNA species of 7.5 kilobases in gill, intestine, muscle, kidney, liver, and brain (Ducouret et al, 1995;Teitsma et al, 1997). Scatchard analysis of the in vitro expressed receptor or its steroid binding domain with tritiated dexamethasone resulted in kilodalton values in the same range as that calculated in binding studies (Knoebl et al, 1996).…”