In the past 20 years that in vitro preparations of central nervous system (CNS) cells have been used to access excitable membrane properties with electrophysiological techniques, there have been remarkable changes both in technology and in knowledge regarding membrane excitability. Patch-type recording techniques are now used routinely because of the exceptionally high fidelity in signal detection afforded by the low resistance access to the properties of excitable membranes. Patch recording techniques permit a detailed study of the elementary changes in ion conduc-tance of single channels detectable in the membrane enclosed by the pipet and systematic study of global changes occurring throughout the recorded cells. The advent of patch-clamp recordings has led to the discovery that rapid, all-or-none transitions in ion conductance are virtually ubiquitous in intracellular and plasma membranes, yet physiologically distributed according to their functional roles. In this Chapter, we will survey in an eclectic manner, a number of contemporary electrophysiological recording techniques commonly used to characterize “chemical” forms of membrane excitability expressed by different cell types.