title: Elevated cortisol inhibits adrenocorticotropic hormone- and serotonin-stimulated cortisol secretion from the interrenal cells of the Gulf toadfish (Opsanus beta).
abstract: Stimulation of the toadfish 5-HT(1A) receptor by serotonin (5-hydroxytryptamine; 5-HT) or 8-OH-DPAT, a 5-HT(1A) receptor agonist, results in a significant elevation in plasma cortisol. Conversely, chronic elevation of plasma cortisol has been shown to decrease brain 5-HT(1A) receptor mRNA and protein levels via the glucocorticoid receptor (GR); however, there appears to be a disconnect between brain levels of the receptor and cortisol release. We hypothesized that elevated plasma cortisol would inhibit both adrenocorticotropic hormone (ACTH)- and 5-HT-stimulated cortisol release from the interrenal cells of Gulf toadfish, that ACTH sensitivity would not be GR-mediated and 5-HT-stimulated cortisol release would not be via the 5-HT(1A) receptor. To test these hypotheses, interrenal cells from uncrowded, crowded, vehicle-, and cortisol-implanted toadfish were incubated with either ACTH, 5-HT or 5-HT receptor agonists, and cortisol secretion was measured. Incubation with ACTH or 5-HT resulted in a stimulation of cortisol secretion in uncrowded toadfish. Cortisol secretion in response to ACTH was not affected in crowded fish; however, interrenal cells from cortisol-implanted toadfish secreted significantly less cortisol than controls, a response that was not reversed upon treatment with the GR antagonist RU486. 5-HT-stimulated cortisol release was significantly lower from both crowded and cortisol-implanted toadfish interrenal cells compared to controls. Incubation with either a 5-HT(4) or a 5-HT(2) receptor agonist significantly stimulated cortisol secretion; however, incubation with 8-OH-DPAT did not, suggesting that the 5-HT(1A) receptor is not a mediator of cortisol release at the level of the interrenal cells. Combined, these results explain in part the disconnect between brain 5-HT(1A) levels and cortisol secretion.
authors.affiliation: Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA. lmedeiros@uidaho.edu
authors.forename: Lea R
authors.initials: LR
authors.lastname: Medeiros
authors.forename: M Danielle
authors.initials: MD
authors.lastname: McDonald
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D024541:Batrachoidiformes; D006854:Hydrocortisone / Q000378:metabolism*; D007401:Interrenal Gland / Q000187:drug effects* / Q000378:metabolism*; D015735:Mifepristone / Q000494:pharmacology; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors; D012701:Serotonin / Q000494:pharmacology*
chemical_list: D011965:Receptors, Glucocorticoid; D015735:Mifepristone; D012701:Serotonin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone