Effect of K+ accumulation removal and high extracellular osmolarity on K+ current in insect axonal membrane

The effect of a removal of K+ accumulation on K+ current in insect axonal membrane was observed. Experiments were performed on isolated giant axon of a cockroach using double oil gap technique. K+ accumulation was reduced by: (1) an outward water flow induced by non-electrolytes (urea, glucose) added to extracellular saline and (2) by an increase of non-specific permeability of axonal glial layer obtained after the application of DMSO. The conclusions are: (1) osmolar effect depends on the type of molecule used for osmotic shock, (2) increase of outward K+ current in conditions of high extraaxonal osmotic pressure is attributed to the decrease of K+ accumulation and outward water flow, (3) removal of K+ accumulation doesn't affect the kinetics and the time course of K+ current, (4) experiments confirmed the presence of an inactivating component in the axonal outward K+ current, (5) DMSO must be used cautiously as a solvent in electrophysiological experiments.