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.
D000818:Animals; D001569:Benzodiazepines / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002243:Carbolines / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003975:Diazepam / Q000378:metabolism; D007476:Ionophores / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011963:Receptors, GABA-A; D013654:Taurine / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002243:Carbolines; D002712:Chlorides; D007476:Ionophores; D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D013654:Taurine; D005680:gamma-Aminobutyric Acid; C028585:propyl beta-carboline-3-carboxylate; D003975:Diazepam