Effects of sodium and bicarbonate ions on gamma-aminobutyric acid receptor binding in synaptic membranes of rat brain.
Crude synaptic membranes treated with Triton X-100 (TX) bound gamma-aminobutyric acid (GABA) to two classes of receptor site in Na+-free 10 mM-Tris-sulfate buffer (pH 7.4), but to only a single class of receptor site in 10 mM Tris-sulfate buffer (pH 7.4), containing 150 mM-NaCl. The high-affinity receptor site in TX membranes was specifically masked in the presence of Na+. However, TX membranes incubated in Krebs-Ringer bicarbonate solution (pH 7.4) bound GABA to two classes of receptor site despite the presence of Na+. It was found that addition of bicarbonate ions to the Na+-containing 10 mM-Tris-sulfate buffer (pH 7.4) could restore that high-affinity class of GABA receptors, rendering both classes detectable. This finding suggests that both Na+ and HCO-3 may have a regulatory function on GABA binding to the receptor.
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011963:Receptors, GABA-A; D012964:Sodium / Q000494:pharmacology*; D013570:Synaptic Membranes / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D001639:Bicarbonates; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D012964:Sodium