Activation of the Cholinergic End-Plate Receptors by Oxidizing Reagents

Abstract

Three types of SH reagents depolarize the end-plate membrane: oxidant agents, organic mercurials and heavy metal ions (Hg++ in particular). The similarity of the effects of such different compounds suggested that whenever certain key SH groups are disturbed or diverted from their free, reduced condition, the receptor protein undergoes a change which results in an increased membrane conductance. We have found that another oxidizing reagent, o-iodosobenzoic acid exerts an extremely powerful and reversible depolarizing action on the end-plate membrane. It was possible, in consequence, to study how d-tubocurarine and tetraethylammonium chloride interfere with its effects. The results obtained suggest that the SH groups which have the ability to induce activation are located at or near the binding site of the cholinergic receptor.