Effect of sulfhydryl group reagents on the crayfish stretch receptor neuron

Abstract

1. The effect of the sulfhydryl group reagents N-ethylmaleimide (NEM), p-hydroxymercuribenzoate (PHMB) and p-hydroxymercuriphenylsulfonate (PHMPS) on ATP content, as well as sodium pump activity and other membrane properties of the crayfish stretch receptor neuron (SRN), has been studied. 2. ATP content of both the SRN and of the nerve segment was significantly decreased by NEM (0.05–1.0 mM), but not by PHMB or PHMPS of similar concentrations. 3. The sodium pump activity as represented by the hyperpolarization which follows intracellular injection of sodium ions was inhibited by all of these reagents. 4. The three sulfhydryl reagents were also found to produce the following electrophysiological changes in the SRN: depolarization of the resting membrane potential, leading to spontaneous firing; change in membrane resistance; decrease in action potential amplitude; and lowering of the triggering level. 5. NEM, at the concentrations used, affected the crayfish SRN and the Aplysia R2 neuron differently. 6. Mechanism of the effect of the SH reagents on SRN function is discussed.