Neuroactive Agents and Nerve Membrane Conductances

Agents that affect nerve excitability may be classed in two large groups according to their mode of action: those which block excitability by depolarizing the membrane, and those which cause little or no change in membrane potential but alter excitability by virtue of their ability to affect the mechanisms whereby the nerve membrane conductances are increased upon stimulation. Because of their possible specific affinity for the nerve membrane channels through which ions flow during excitation, the latter group of neuroactive agents is of particular interest from the electrophysiological point of view. The present paper is concerned with studies of the manner in which various types of neuroactive agents affect excitability through interactions with the membrane conductances, and an at tempt is also made to characterize the properties of ionic channels of the nerve membrane by use of these agents.