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MSc Exit Seminar – Ashley Miles (Buck lab)
April 3, 2017 @ 10:10 am
MSc Exit Seminar
Monday April 3rd, 10:10 am – Ramsay Wright Building, Rm. 432
Ashley Miles (Buck lab)
“The inhibitory role of taurine through glycine and GABAA receptors in the anoxia-tolerant western painted turtle brain (Chrysemys picta bellii)“
Abstract
Unlike the anoxia-intolerant mammalian brain, the western painted turtle Chrysemys picta bellii can survive extended periods of anoxia without apparent neuronal damage. This is partly accomplished by a large increase in the levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), resulting in suppression of spontaneous electrical activity (i.e. spike arrest) via shunting inhibition and a decrease in ATP-consumption. Additionally, taurine levels increase, but its function within the anoxic turtle brain is unknown. It is speculated that taurine can function like an inhibitory neurotransmitter, acting through glycine and/or GABAA/B receptors. Given the important role of inhibition in anoxia-tolerance, we wanted to investigate the possible role of taurine as an inhibitory molecule in the anoxia tolerant western painted turtle brain. Using the whole cell patch clamp technique, we measured the response of neurons to taurine. We found that taurine caused the membrane potential of neurons to depolarize approximately 8mV, similar to the effects of the other inhibitory molecules, GABA and glycine, and mimicking anoxia. Additionally taurine increased whole cell conductance >2-fold and induced a current consistent with an efflux of Cl– ions. Compared to GABA and glycine application however, recovery from taurine application was significantly slower indicating a difference in kinetics and possibly a difference in mechanisms of actions. To test the receptor(s) taurine could be acting through to mediate its effects, we used a number of pharmacological inhibitors. We found that taurine’s effects were reduced when the glycine antagonist, strychnine, and the GABAA receptor blockers, gabazine, bicuculline and picrotoxin, were applied but not when GABAB or glutamatergic receptors were inhibited, indicating that taurine activates glycine and GABAA receptors to mediate its effects. Together these results suggest that taurine acts through both glycine and GABAA receptors to affect turtle cortical neurons and therefore may act as an inhibitory signaling molecule during anoxia in the turtle cortex.
Ramsay Wright is a wheelchair accessible building.