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Taurine Modulation of the Benzodiazepine‐γ‐Aminobutyric Acid Receptor Complex in Brain Membranes
Author(s) -
Medina †Jorge H.,
Robertis Eduardo
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb02774.x
Subject(s) - taurine , flunitrazepam , inhibitory postsynaptic potential , chemistry , gabaa receptor , aminobutyric acid , gabaergic , benzodiazepine , receptor , biochemistry , amino acid , biology , endocrinology
In unwashed brain membranes taurine produced an inhibition of [ 3 H]flunitrazepam ([ 3 H]FNZ) binding with IC 50 ranging between 31.5 and 11.9 μ M ; the IC 20 varied between 18 and 26 n M . This inhibitory effect was of a mixed type, with a reduction in B max and an increase in K D . Various precursors and metabolites of taurine have a less inhibitory effect. Taurine also has little inhibitory effect (IC 50 above 500 μ M ) on the binding of [ 3 H]ethyl‐β‐carboline‐3‐carboxylate. In extensively washed membranes, 10 −5 M taurine produces a 16–21% increase in the binding of [ 3 H]FNZ while 10 −5 M γ ‐ami‐nobutyric acid (GABA) increases it between 31 and 42%. However, if 10 −5 M GABA plus 10 −5 M taurine is included in the assay there is a dramatic inhibitory effect. Taurine causes an inhibition of the GABAergic enhancement of [ 3 H]FNZ binding with an IC 50 between 7.3 and 7.8 μ M . Binding experiments with [ 3 H]taurine done under different conditions failed to detect a Na + ‐independent and specific [ 3 H]taurine receptor. These results suggest that endogenous taurine, the second most abundant free amino acid in brain, may play an important modulatory role in the GABA‐benzodiazepine receptor complex.