Neuroplasticity

by Moheb Costandi

The induction of LTP is dependent upon binding of the excitatory neurotransmitter glutamate to N-methyl-D-aspartate (NMDA) receptors. The NMDA receptor is an ion channel that is permeable to sodium, potassium, and calcium, but the central pore that allows these ionic currents to pass is blocked by a magnesium ion. Under normal circumstances, this magnesium block remains, and the glutamate released from a nerve terminal works through two other receptor types, the AMPA and kainate receptors. High-frequency stimulation of the kind that induces LTP increases the amount of glutamate released by the nerve terminal and removes the magnesium block, allowing currents to flow through the NMDA receptors. The influx of calcium is particularly important, as it triggers various enzymes needed for the cellular processes underlying LTP.