Effect of taurine on a benzodiazepine-GABA-chloride ionophore receptor complex in rat brain membranes.

Taurine at 10 mM had no effect on basal binding of [3H]diazepam to the membranes, while it significantly inhibited a GABA-stimulated binding of [3H]diazepam in cerebral cortex, hippocampus, but not in cerebellum. The inhibition by taurine in the presence of GABA (1 microM to 1 mM) was not competitive. At low concentrations (0.04 to 0.2 nM) the binding of [3H]propyl-beta-carboline-3-carboxylate, a ligand exhibiting higher affinity for type I than type II benzodiazepine receptors, was not enhanced by GABA, while the binding of higher concentrations (0.5 nM) was. This GABA enhancement of [3H]propyl-beta-carboline-3-carboxylate binding was also selectively blocked by taurine. Pentobarbital increased the binding of [3H]diazepam in a medium containing chloride and this effect was potentiated by taurine at 1-10 mM. These findings may be relevant to the modulatory role of taurine in the central nervous system.