Glutamate Receptor GluR-Kl: Structure, Function, and Expression in the Brain

Abstract

The excitatory action of l-glutamate (GLU) on neurons, discovered more than 35 years ago (Hayashi 1954), has become the focus of considerable research interest. Although initially controversial, it is now generally accepted that excitatory amino acids (EAA) serve as neurotransmitters at the majority of all excitatory synapses in the brain (Monaghan et al. 1989). At least five pharmacologically different glutamate receptor subtypes have been recognized on the basis of their differential sensitivities to a variety of antagonists. These subtypes have been named NMDA (N-methyl-d-aspartate), KA (kainate), AMPA (α-amino-3-hydroxy-5-methyl-isooxazol-4-propionate), AP4 (l-2-amino-4-phosphono butyrate), and ACPD (1-amino-cyclopentyl-1,3-dicarboxylate), with the names derived from the most active agonists that have been discovered for each subtype (Monaghan et al. 1989). The first four of these receptor subtypes are referred to as ionotropic or type I receptors (Strange 1988) because they contain integral, ligand-gated ion channels. The AMPA subtype formerly was called the QA (quisqualate) receptor. The...