How does LTP work?
LTP involves two types of glutamate receptors-- NMDA receptor and AMPA receptor. Before LTP begins, the presynaptic neuron is releasing glutamate which opens the NMDA glutamate receptors on postsynaptic membrane, which, depite being open, are blocked. However, when other synapses on the postsynaptic cell depolarize the postsynaptic membrane, the NMDA receptors become unblocked, causing an influx of calcium and sodium ions. The calcium influx triggers the insertion of AMPA glutamate receptors into the postsynaptic membrane. Once this occurs, glutamate release by the presynaptic neuron activates AMPA receptors that trigger depolarization, which leads to the unblocking of NMDA receptors. Together, both NMDA and AMPA receptors trigger postsynaptic potentials strong enough to initiate action potentials without input from other synapses.