Electrophysiological Methods for Studying Ionic Currents in Brain Slices and Cell Cultures

The last two decades have seen a tremendous explosion in our knowledge concerning the properties of neurons of the central nervous system (CNS). The basis of this explosion is twofold: one is the development of the methodology to maintain isolated slices of brain tissue alive, and the second is the discovery of pharmacological tools to alter specific ionic channels of neurons. Some pioneering work describing neuronal electrophysiology has also been done on neurons cultured in slice preparations or after dissociation. The purpose of this chapter is to briefly describe the methodologies involved in maintaining isolated brain slices and cultures of both slices and dissociated cells and to describe the experimental paradigms that have been developed in the last few years to determine the ionic currents underlying the electrophysiological properties of the mammalian CNS. Also, another important area of research will be discussed: the measurement of extracellular ion concentrations in the CNS and the dynamic changes that occur during neuronal activity. Much of this work has been done in vivo, but extracellular and intracellular ion measurements have also been made in brain slice preparations, Because of the complexity of the intact CNS, there are few experiments correlating extracellular ionic changes with intracellular ionic currents.