Facilitation of benzodiazepine binding by sodium chloride and GABA

An endogenous substance was found which facilitated benzodiazepine binding and was subsequently identified as GABA. The facilitation of benzodiazepine binding produced by GABA obeyed Michaelis — Menten Kinetics and Scatchard analysis revealed that this facilitation was due to an increased affinity of the benzodiazepine receptor. Sodium chloride itself increased benzodiazepine binding and also markedly enhanced the facilitation caused by GABA, by a further increase in the affinity of the benzodiazepine receptor. The enhancement of the GABA effect produced by sodium chloride showed sigmoidal kinetics indicating cooperativity, no evidence could be found for the involvement of sodium-dependent GABA binding in this interaction.