Ammonium salts of some anions decrease the potency of glycine in inhibiting [³H]strychnine binding associated with synaptic glycine receptors. A correspondence exists between the ability of the ammonium salts of anions to increase the IC₅₀ of glycine in inhibiting the [³H]strychnine binding, their capacity to reduce the [³H] strychnine binding itself, and their capacity to reverse inhibitory postsynaptic potentials. The decrease of [³H]strychnine binding in the presence of chloride is abolished by sodium, while the decrease of the potency of glycine in inhibiting [³H]strychnine is not. Binding of [³H]strychnine is influenced by monovalent cations in a biphasic fashion. Concentrations of Li⁺, K⁺, and Na⁺ up to 150 mM decrease [³H]strychnine binding, while higher concentrations of the cations increase [³H]strychnine binding. Inhibition by glycine of [³H]strychnine binding is enhanced by low concentrations of these cations.