Taurine Regulation of Voltage-Gated Channels in Retinal Neurons
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Taurine activates not only Cl−-permeable ionotropic receptors but also receptors that mediate metabotropic responses. The metabotropic property of taurine was revealed in electrophysiological recordings obtained after fully blocking Cl−-permeable receptors with an inhibitory “cocktail” consisting of picrotoxin, SR95531, and strychnine. We found that taurine’s metabotropic effects regulate voltage-gated channels in retinal neurons. After applying the inhibitory cocktail, taurine enhanced delayed outward rectifier K+ channels preferentially in Off-bipolar cells, and the effect was completely blocked by the specific PKC inhibitor, GF109203X. Additionally, taurine also acted through a metabotropic pathway to suppress both L- and N-type Ca2+ channels in retinal neurons, which were insensitive to the potent GABAB receptor inhibitor, CGP55845. This study reinforces our previous finding that taurine in physiological concentrations produces a multiplicity of metabotropic effects that precisely govern the integration of signals being transmitted from the retina to the brain.
KeywordsBipolar Cell Channel Current Amacrine Cell GABAB Receptor Retinal Neuron
Inner plexiform layer
Outer nuclear layer
Inner nuclear layer
Ganglion cell layer
This work was supported by research grants to W.S. from NSF (1021646) and NIH (EY14161).
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