The GABA receptor complex contains binding sites for GABA, benzodiazepines, and barbiturates. It was believed that there were increased levels of GABA and endogenous benzodiazepines in plasma. These chemicals would then cross an extrapermeable blood-brain barrier. Binding of GABA and benzodiazepines to a supersensitive neuronal GABA receptor complex permitted the influx of chloride ions into the postsynaptic neuron, leading to generation of an inhibitory postsynaptic potential.