The influence of cardioactive steroids, metabolic inhibitors, temperature and sodium on membrane conductance and potential of crayfish giant axons

Abstract

The resting membrane potential and the current-voltage relation were measured in crayfish giant axons before and after treatment with cardioactive steroids, metabolic inhibitors, extracellular sodium depletion and low temperature. The membrane resistance of axons treated with cardioactive steroids, metabolic inhibitors, and low extracellular sodium was reduced by 30–53% depending on the treatment. Low temperature also caused a decrease in the membrane resistance of the axon but the decrease was limited to potentials around the resting membrane potential. The temperature response of sodium depleted or ouabain treated axons was an increase in resistance at all points along the current-voltage relation. All inhibitors and low temperature caused a depolarization of the membrane potential. Ouabain and strophanthidin were the most effective, reducing the membrane potential by an average of 9.6 mV in 10–20 min. Low sodium did not cause a depolarization but consistently reduced the membrane resistance by an average of 30%. The data suggest that there is an interaction between the activity of the ouabain-sensitive transport system and resting membrane resistance in the crayfish axon.