Chapter V Regional and synaptic expression of ionotropic glutamate receptors

Abstract

This chapter reviews the ionotropic glutamate receptor distribution in the brain and other organs, and discusses the factors affecting the expression of ionotropic glutamate receptors in synapses, mainly in the postsynaptic spine. Ionotropic glutamate receptors are made up of complexes of four or five subunits forming a central ion channel that passes sodium or calcium ions. They include the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors with four subunits, GluR1–4, the kainate receptors with five subunits, GluR5-7 and KA1-2; the delta receptors with two subunits, delta 1–2 (δ 1-2), and the N-methyl-D-aspartate (NMDA) receptors with six subunits, NR1, NR2A–D, and NR3. Many subunits also have variant forms generated through alternative splicing. Different subunits within each group usually combine to form heteromeric receptor complexes, although homomeric complexes made entirely of one kind of subunit also occur. Thus, fully functional NMDA receptors require NR1 plus at least one kind of the NR2 subunits, while AMPA receptors can be heteromeric or homomeric complexes.