Using electrophysiology to study synaptic and extrasynaptic ionotropic receptors in hippocampal neurons

Abstract

Electrophysiology is an exceptionally useful tool for neuroscience research due to the intrinsic electrical excitability of neurons and the significant array of ion channels present in both neurons and glia. Diverse electrophysiological techniques may be applied to neurobiology ranging from measurements of cell populations in broad brain regions to measurements of single channels in patches of plasma membrane. One of the strengths of electrophysiology as a tool is the ability to measure the properties of known ion channels in heterologous systems, then dissect the diverse pharmacology and biophysics of neuronal responses to finally better understand which component channels and their features determine the biologically critical outputs of neurons and circuits. Patch-clamp electrophysiology allows recording of neuronal receptors at both the synaptic and extra-synaptic level. The specific techniques described here permit the study of both populations independently by measuring miniature excitatory synaptic currents and currents derived from somatic receptors. The resolution and accuracy of the techniques described in the chapter are high (in the sub-picoampere and sub-millisecond ranges). Further, these methodologies provide valuable information about the behavior of the receptors in their native environment where they coexist with auxiliary, modulatory, and anchoring proteins. In this chapter, we firstly describe the methodology for preparing hippocampal neuronal cultures. Secondly, we describe the process of recording and analyzing miniature postsynaptic currents. Finally, we describe in detail the technique of fast agonist application onto outside-out patches obtained from the soma of neurons. We discuss common problems found with these approaches and present tips to assist researchers new to the field so they may rapidly master the techniques.