POTASSIUM CHANNELS IN GROWTH CONES OF LEECH RETZIUS CELLS

1. Potassium-selective channels were analysed in growth cones of cultu red leech Retzius cells. 2. In the cell-attached mode and at physiolog ical bath and pipette solution little channel activity was observed at resting membrane potential. The channel open probability (p(o)) incre ased with cell depolarization, and the slope conductance of the single K+ channel current was about 60 pS. 3. With symmetrical high KCl solu tion on both sides of the excised membrane patch three K+-selective ch annels could be discriminated. Two channels exhibited a linear current -voltage relation of about 18 pS and 106 pS, respectively. 4. The most frequently observed K+ channel showed a non-linear current-voltage re lation and p(o) increased with increasing free cytoplasmic Ca2+ and du ring cell hyperpolarization.