Significant potassium ion accumulation at the external surface of Myxicola giant axons.
Potassium accumulation associated with outward membrane potassium current was investigated experimentally in Myxicola giant axon. During prolonged voltage-clamp pulses to positive transmembrane potentials, the K+ equilibrium potential may approach zero mV, suggesting massive K+ accumulation outside the axonal membrane to concentrations many-fold higher than those in the bathing medium. The potassium accumulation can be satisfactorily described by a three-compartment model, consisting of the nerve fiber, a restricted physiological periaxonal space and the bulk solution. The average thickness, theta, of the periaxonal space is calculated as 177 +/- 59 A, i.e., comparable to that in the squid, while the permeability coefficient of the external barrier, PKs, was calculated to be (1.4 +/- 0.4) X 10(-4) cm/s. These conclusions are well supported by morphological study.
D000818:Animals; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure; D002414:Cations, Monovalent; D049832:Decapodiformes; D004553:Electric Conductivity; D004594:Electrophysiology; D008564:Membrane Potentials; D008854:Microscopy, Electron; D008954:Models, Biological; D010539:Permeability; D011077:Polychaeta / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*
D002414:Cations, Monovalent; D011188:Potassium