Direct and rapid description of the individual ionic currents of squid axon membrane by ramp potential control.

Computations based upon the Hodgkin-Huxley equations and experimental data from squid axons show that ramp functions can be used as commands to a voltage clamp system to selectively observe either the fast (sodium) or slow (potassium) process in axon membranes without chemical separation techniques or computer assistance. Each process is characterized directly (on line) and rapidly (real time) by generating a current-potential curve on an oscilloscope for fast or slow rates of change of membrane potential (ramps). The speed and directness of this method of characterizing each of the essential axonal events permit quantitative measurement of the kinetics of rapid effects on these processes due to various pharmacological agents such as tetrodotoxin and tetraethylammonium ion or other experimental changes in the membrane environment.