Peter H. Seeburg (Center for Molecular Biology, University of Heidelberg): "In our brain, nerve cells communicate by chemical transmission at specialized structures termed synapses. Most excitatory synapses use the neurotransmitter L-glutamate, which activates specific receptor channels in the postsynaptic membrane. Molecularly and functionally different glutamate-activated channels are expressed by the brain, presumably tailored to the requirements of the particular synapses carrying them. The N-methyl-D-aspartate (NMDA) receptor is one of these channels and is a major mediator of excitatory neurotransmission. Its properties are high permeability for Ca2+ and slow gating kinetics. Moreover, this receptor channel is blocked by extracellular Mg2+ ions.
"The strength of this block depends on the membrane potential. Around the cell's resting potential the block is in place; upon excitation and, hence, the neuron depolarization of the cell's membrane, the block is released and the channel activated by glutamate can flux Ca2+ ions. Ca2+ ions entering the cell ...
