Potassium channels in growth cones of leech Retzius cells

1. Potassium-selective channels were analysed in growth cones of cultured leech Retzius cells. 2. In the cell-attached mode and at physiological bath and pipette solution little channel activity was observed at resting membrane potential. The channel open probability (p(o)) increased with cell depolarization, and the slope conductance of the single K+ channel current was about 60 pS. 3. With symmetrical high KCl solution on both sides of the excised membrane patch three K(+)-selective channels 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 relation and p(o) increased with increasing free cytoplasmic Ca2+ and during cell hyperpolarization.