Two types of calcium-dependent channels of potassium outward current in the somatic membrane of Helix pomatia neurons

Characteristics of delayed potassium outward current were investigated during voltage clamp experiments on nonidentified intracellularly perfused neurons isolated from the snailHelix pomatia. A calcium-dependent potassium curent displaying special properties was shown to exist, apart from the voltage-operated potassium currents dependent on intracellular calcium ions . This type of current increases with a rise in the extracellular concentration of calcium ions , is not blocked by intracellular application of 10 mM EGTA and 77 mM fluoride, and may be suppressed by adding 1.5 mM cobalt ions to the extracellular fluid. This current, unlike , only takes a few milliseconds to peak, after which it fades to a steady level, comparable with that of .A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 185–191, March–April, 1987.