Anion dependent swelling of crab nerve fibers during potassium- and veratridine depolarization.

Swelling of crab claw nerve fibers, monitored as weight increase, takes place while the nerve fibers are immersed in a medium high in K+, Cs+ or Rb+ concentration, or in artificial seawater to which 0.2 mM veratridine is added. Similar swelling is observed in nerves in sodium salt solutions which also contain low concentrations of divalent cations. The swelling observed under these conditions is dependent on anions, giving a series (from efficient anion to less efficient ones): I- greater than SCN- greater than Br- greater than Cl- much greater than F- greater than glutamate, ethylsulfate. The presence of this series indicates that the nerve swelling observed is attributed to influx of external salt. Uptake measurements of radioactive anions and cations corroborate the presence of salt influx under these conditions. In analyzing the anion dependence of nerve swelling, two factors, membrane and cytoskeletal structure, are examined. It is shown that the cytoskeletal structure, which is sensitive to the lyotropic series of anions, plays an important role in this phenomenon.