Penetration of Non-Electrolyte Molecules in Resting and Stimulated Squid Nerve Fibers

The experiments to be described deal with the penetration of C4-labeled erythritol, mannitol, and sucrose in resting and stimulated axons of the squid Doryteuthis plei. The results indicate an increase in the penetration of the nonelectrolytes in the stimulated axons. This increase may be due either (a) to a change in the structure of the axolemma or (b) to a drag effect of the sodium ions entering the axon during the nerve impulse, since sodium entry is larger during stimulation. Experiments on the effects of high potassium and low sodium concentrations in the extracellular fluid on the penetration of C14erythritol also are described. Some recent sodium entry measurements are reported (1).