SEMINAR: MBF602 10/7/11 S/A 103, 1:00pm Lea R. Medeiros: Keeping the balance: 5-HT1A, cortisol, and the stress response in the Gulf toadfish (Opsanus beta)

["Maxine Williams" <mwilliams@rsmas.miami.edu>]

MBF602 10/7/11 S/A 103, 1:00pm Student Speaker Lea R. Medeiros

 

Keeping the balance: 5-HT_1A, cortisol, and the stress response in the Gulf toadfish (Opsanus beta)

 

When serotonin (5-HT) or 8-OH-DPAT binds to the toadfish 5-HT_1A receptor, they result in a significant elevation in plasma cortisol through the stimulation of the hypothalamic-pituitary-interrenal (HPI) axis.  Conversely, chronic elevation of plasma cortisol has been shown to mediate changes in brain 5-HT_1A receptor mRNA and protein levels via the glucocorticoid receptor; however, there appears to be a disconnect between brain levels of the receptor and activation of cortisol release from the interrenal tissue.  To investigate this, interrenal cells from stressed and unstressed toadfish were incubated with adrenocorticotropin hormone (ACTH) or 5-HT and cortisol secretion was measured.  When stimulated with ACTH, interrenal cells from crowded toadfish (plasma cortisol ~200 ng·mL^-1) tended to secrete less cortisol than the uncrowded treatment (cortisol ~25 ng·mL^-1), while cortisol-implanted toadfish (cortisol ~1000 ng·mL^-1) did secrete significantly less cortisol than controls.  While incubation with 5-HT did significantly stimulate cortisol secretion, treatment with 8-OH-DPAT did not.  These results suggest that chronically elevated plasma cortisol attenuates cortisol secretion from the interrenal cells of toadfish and the 5-HT_1A receptor is not a mediator of cortisol release at the level of the interrenal cells, explaining in part the disconnect between brain 5-HT_1A levels and HPI axis function.

 

Lea R. Medeiros

Occidental College, B.A. Biology 2005

Entered Ph.D. program Fall of 2007

Advisor: Danielle McDonald