NMDA receptor kinetics and synaptic function

Presynaptic release of L-glutamate mediates neurotransmission at most excitatory synapses in the vertebrate central nervous system. At the postsynaptic membrane, glutamate binds to two classes of ligand-gated ion channels, AMPA receptors and NMDA receptors. These channels are the basis of the two kinetically distinct components of the excitatory postsynaptic current (epsc). The slower synaptic conductance is mediated by NMDA receptor channels which, after binding glutamate, activate slowly and can remain activated for several hundred milliseconds. The average latency between glutamate binding and channel opening is at least several milliseconds and may be much longer. If the time to first opening is short many fewer channels would be required at each synaptic site to account for the amplitude of the NMDA receptor component of spontaneous miniature epscs, than if the time to first opening is very long.