Influences of ions, enzymes, and detergents on γ aminobutyric acid receptor binding in synaptic membranes of rat brain

The effects of ions, detergents, and enzymes on γ aminobutyric acid (GABA) binding to synaptic receptor sites in membranes of rat brain in the absence of sodium is contrasted with influences on sodium dependent GABA binding. The anions thiocyanate, iodide, and nitrate increase the potency of the GABA antagonist bicuculline 10 fold in inhibiting sodium independent GABA receptor binding without affecting the potency of GABA agonists. Very low concentrations of the detergent Triton X 100 increase sodium independent GABA receptor binding up to 5 fold. In the presence of Triton X 100, GABA receptor binding can be detected with considerable sensitivity using fresh or previously frozen tissue in the presence of sodium, facilitating studies of GABA receptors in small tissue samples and increasing the sensitivity of radioreceptor assays for endogenous GABA.