Wednesday, October 12, 2011
Glutamate-gated Ion Channels
Glutamate-gated ion channels are excitatory amino acid receptors of the nerve cells of the brain, which are classified according to the synthetic ligands binding to them. There are three types of glutamate-gated ion channels: the AMPA (aminohydroxymethylisoxazolepropionic acid) receptor (C3), the NMDA (Nmethyl-D-aspartate) receptor (C4), and the kainate receptor. Binding to the AMPA receptor causes an influx of sodium ions, thus leading to depolarization of the cell. Similarly, activation of the NMDA receptor causes an influx of both Na+ and Ca2 +. Under conditions of resting potential, the NMDA receptor is blocked by magnesium; the magnesium blockade is lifted by depolarization (through AMPA receptors). This temporal shift in activities of the AMPA and NMDA receptors results in a graduated response of the postsynaptic neurons to the neurotransmitter glutamate.