SEMINAR: FW: MBF602 9/30/11 S/A 103, 1:00pm Alex Frere: The Variation of mRNA Expression and Binding Kinetics of 5-HT2A Receptor, in the Gulf Toadfish, Opsanus beta in Response to Stress

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

MBF602 9/30/11 S/A 103, 1:00pm Student Speaker Alex Frere

The Variation of mRNA _expression_ and Binding Kinetics of 5-HT2A Receptor, in the Gulf Toadfish, Opsanus beta in Response to Stress

 

On any given patch of seagrass in Biscayne Bay, there are toadfish. Becoming the third most common species in the Bay was not easy for these cranky croakers; they had to develop a complicated cloaking mechanism. Benthic predators demonstrate an ability to locate prey based on their ammonia waste. By cloaking their nitrogenous waste as distinct pulses of urea rather than continuous ammonia excretion, stressed toadfish may avoid detection. I investigate hormonal and neural control of urea excretion in toadfish. Injection with the serotonin type 2 (5-HT2) receptor agonist, Î-methyl 5-HT, initiates a urea pulse, while injections with the 5-HT2A receptor antagonist, ketanserin, can block the 5HT-induced appearance of urea. Investigating differences in 5-HT2A receptor mRNA _expression_ and binding kinetics between unstressed and chronically stressed toadfish may help show why cortisol inhibits this pulse. Ketanserin binding shows that crowded fish have a higher Bmax and Kd (79922Â7070 fmolÎmg-1 protein and 1.28 Â 0.22 x 10-8M) than uncrowded fish (39395Â1577 fmolÎmg-1 protein and 5.529Â0.3 x 10-9M, p=0.0015). This suggests a shift from fewer high-affinity receptors to more low-affinity receptors in response to stress; as ketanserin does not solely target 5-HT2A (ketanserin preferentially binds to 2A over 2C and 2B), a change in overall receptor population may be occurring.

 

Alex Frere

B.S. in both Biopsychology and Biomedical Engineering, Tufts University 2007

Entered MBF June 2010

Advisor: Danielle McDonald