Potassium channels in Myxicola giant axons

This article describes an initial step in the study of potassium ion (K+) channel properties and their role in the control of patterns of action potential frequency. The purpose of the study was to determine the effect of the K+ channel blocker 4-aminopyridine on the conductance of the K+ channels in Myxicola. If this pharmacologic agent modifies one or more of the multiple kinetic components of the K+ channel conductance, it may be expected to alter the physiological properties of normal and pathological nerve fibers. Experiments were performed on 19 internally perfused voltage-clamped Myxicola infundibulum giant axons. After accounting for the time-dependent accumulation of K+ in the surrounding periaxonal spaces, the K+ conductance activates biphasically. The external application of 4-aminopyridine (20 mmol/L) specifically blocks the fast component of activation of the K+ conductance.