The Inhibitory Role of Taurine through Glycine and GABAA Receptors in the Anoxia-tolerant Western Painted Turtle Brain (Chrysemys picta bellii)

Unlike anoxia-intolerant mammals, painted turtles survive extended periods of anoxia. This is partly accomplished by an increase in gamma-aminobutyric acid (GABA) which mediates spike arrest via shunting inhibition in brain. Taurine levels also increase; its purpose is unknown but is speculated to include actions similar to inhibitory neurotransmitters, acting through glycine and/or GABAA/B receptors. Given the general importance of inhibition in anoxia-tolerance, we investigated taurineâ s function as an inhibitory molecule in the turtle cerebrocortex. Using whole-cell patch-clamp electrophysiological methods we found that taurine depolarized membrane potential, increased whole cell conductance and induced an inward current similar to the effects of GABA and glycine. These effects were reduced when glycine and GABAA receptors but not GABAB or glutamatergic receptors were inhibited, suggesting that taurine mediates its effects through both glycine and GABAA receptors. Therefore, taurine may act as an inhibitory signaling molecule during anoxia in the turtle cortex.M.Sc.2019-11-08 00:00:0