Modulation of human GABArho1 receptors by taurine.
A study was made of the effects of taurine on GABArho1 receptors expressed in Xenopus oocytes. The EC(50) and reversal potentials for GABA, taurine and glycine currents were 2.3+/-0.4 microM (-25+/-0.9 mV), 5+/-0.8mM (-27+/-0.4 mV) and 7+/-0.5mM (-22+/-0.6 mV), respectively. Co-application of GABA and taurine, revealed a taurine concentration-dependent biphasic-modulation of the receptor: at 0.3-30 microM taurine potentiated the GABA-currents, whereas at 0.3-30 mM the GABA-currents were reduced. In contrast glycine potentiated the GABA-currents at all concentrations tested. TPMPA, a GABA(C) specific receptor antagonist, also blocked effectively and reversibly the taurine and glycine currents. Finally, lanthanum and zinc modulated the currents generated by the three amino acids. Taurine is abundant in the retina and our observations suggest that taurine may play an important role modulating the retinal GABAergic transmission.
Ochoa-de la Paz
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Departamento de Neurobiología Molecular y Celular, Laboratorio de Neurobiología Molecular y Celular II, Instituto de Neurobiología, Campus Juriquilla-UNAM Boulevard Juriquilla 3001, C.P. 76230 Juriquilla, Qro., Mexico.
Martínez-Dávila
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IA
Miledi
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Martínez-Torres
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D000818:Animals; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D005998:Glycine / Q000494:pharmacology; D006801:Humans; D020128:Inhibitory Concentration 50; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D008845:Microinjections; D009865:Oocytes; D018408:Patch-Clamp Techniques / Q000379:methods; D018079:Receptors, GABA / Q000502:physiology*; D013654:Taurine / Q000494:pharmacology*; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018079:Receptors, GABA; D013654:Taurine; D005680:gamma-Aminobutyric Acid; D007811:Lanthanum; D015032:Zinc; D005998:Glycine