The ionotropic glutamate receptors (iGluRs) constitute the second class of neurotransmitter- activated LGICs. Three major classes of iGluRs exist, the AMPA receptors (AMPARs, gene name GRIA, made by GluRs1-4), the NMDA receptors (NMDARs1-3, gene name GRIN), and the kainate receptors (KARs, made by GluRs5-7 and KAs1-2, gene name GRIK). These receptors are now thought to be tetrameric and each subunit contains a large N-terminal domain and an extracellular loop domain that together participate in ligand binding via a “venus fly-trap” motif (Gouaux 2004). The subunits have three membrane-spanning domains and a re-entrant pore-loop that forms the ion conduction pathway, as well as intracellular loops and a large intracellular C-terminal domain. The iGluRs are all cationpermeable, with varying ratios of Na+, K+ and Ca2+ selectivity. These receptors are present on all CNS neurons, where they mediate fast synaptic transmission and activation of intracellular signaling.
