15 - Characterization of Glutamate Receptor Function Using Calcium Photometry and Imaging

Abstract

Publisher Summary This chapter discusses characterization of the glutamate receptor function using calcium photometry and imaging. Glutamate is a ubiquitous amino acid neurotransmitter in the mammalian central nervous system. Activation of glutamate receptors can cause changes in the intracellular concentration of free Ca 2+ ions ([Ca 2+ ] i ) by direct permeation of Ca 2+ through the receptor–channel complex, by modulation of voltage-gated Ca 2+ channel activation, or by causing release of Ca 2+ from intracellular stores. There are two broad families of ionotropic glutamate receptors—the N -methyl- d -aspartate (NMDA) and the non-NMDA receptors. The ionotropic glutamate receptor subunits gate cation channels and have molecular structural characteristics of ligand-gated channels. When functionally expressed in oocytes or cell lines, ionotropic subunits display diverse properties. The chapter explains why Ca 2+ -sensitive dye recording is well suited for the study of glutamate receptor function and presents two different approaches to [Ca 2+ ] i measurement using two dyes: indo-1 and fura-2. The NMDA and non-NMDA ionotropic glutamate receptors are receptor–channel complexes that open following ligand binding and allow cation flow across the membrane; the monovalent cations Na + and K + permeate these channels. In the case of the NMDA receptor and some configurations of the non-NMDA receptors, the divalent cation Ca 2+ also permeates these channels.