Na+-independent binding of GABA to the triton X-100 treated synaptic membranes from cerebellum of rat brain |
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Authors: | David T. Wong Jong S. Horng |
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Affiliation: | The Lilly Research Laboratories, Eli Lilly and Company Indianapolis, Indiana 46206, USA |
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Abstract: | The treatment of the membranes from cerebellum of rat brain with 0.5% Triton X-100 increases both the affinity and the density of the Na+-independent binding sites for 3H-GABA (γ-aminobutyric acid) from the values obtained from membranes of rat brain after an extensive freezing and thawing treatment (Young , 1976). Upon repeated washings of the Triton-treated membranes, the binding of 3H-GABA is further increased and follows biphasic kinetics which indicates two binding components having dissociation constants of 5.9 and 27 nM and densities of 1.35 and 3.9 pmole/mg protein, respectively. GABA agonist, imidazoleacetic acid, and the GABA antagonists, bicuculline and d-tubocurarine, inhibit 50% of 3H-GABA binding at 1, 47 and 85 μM concentrations (IC50 values), respectively. The IC50 values for these compounds are unchanged by Na+. Thus, the Na+-independent binding of 3H-GABA to the Triton-treated membranes may represent binding to the synaptic GABA receptors. |
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