Two types of K+ channels in excised patches of somatic membrane of the leech AP neuron.

The patch-clamp technique has been applied to the somatic membrane of the leech AP neurons. Ionic currents from single potassium channels were recorded in inside-out configuration. Two types of channels, sharing close values of conductance in symmetrical K+, were identified as distinct, according to their properties of rectification, Ca2+ sensitivity and voltage dependence. The channels designated as VCI exhibited an outward rectification and their gating was quite independent on changes of patch potential and of [Ca2+]i. The channels designated as VCD showed a linear I-V relationship and their activity was dependent on both the membrane potential and the intracellular [Ca2+].