Are sulfhydryl groups essential for function of the glutamate-operated receptor-ionophore complex?

We monitored glutamate- or kainic acid-induced inward currents in pyramidal neurons of the rat hippocampus to determine a possible chemical modification of sulfhydryl residues on glutamate-receptor-ionophore complexes. Organic and inorganic mercury compounds such as HgCl2 and n-chloromercuribenzoate, 5,5'-dithiobis (2-nitrobenzoic acid) and N-ethylmaleimide depressed glutamate- or kainate-induced responses while the mercury compounds inhibited the kainate response, in a non-competitive manner. The responses inhibited by these agents were dose-dependently recovered by adding cysteine or glutathione. These observations suggest that the excitatory glutamate-receptor-ionophore complex includes sulfhydryl residues, components which may play a role in related functions.