The taurine uptake inhibitor guanidinoethyl sulphonate is an agonist at gamma-aminobutyric acid(A) receptors in cultured murine cerebellar granule cells

In patch clamp experiments the p-amino acid uptake inhibitor guanidinoethyl sulphonate (GES) activated currents in intact cultured murine cerebellar g ranule neurones. These responses could be attenuated by the gamma-aminobuty ric acid(A), (GABA(A)) receptor antagonists bicuculline and picrotoxin, Wit h intracellular chloride concentrations of either 20 or 130 mM, GES-induced current responses reversed polarity near the chloride equilibrium potentia l. When fast applications of agonist were made to excised granule cell macr opatches GES responses were dose-dependent and exhibited significant outwar d rectification. Like taurine (but unlike GABA and P-alanine) responses, ma croscopic desensitisation of GES-induced currents was slow. Our data indica te that care should be exercised when using GES as a taurine uptake inhibit or in systems that also contain GABAA receptors. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.