NMDA receptor

NMDA receptors are glutamate-gated ion channels that are central to communication between neurons [2]. When the receptor is activated, a channel opens through the cell membrane and lets charged particles, including calcium, flow in [1]. These receptors carry a calcium-permeable part of excitatory signaling in the central nervous system, and they are found throughout it [1].

Each receptor is built from four subunits. There are seven kinds of subunit (GluN1, GluN2A-D and GluN3A-B), and different combinations give receptor subtypes with different properties [1]. Researchers are still working out whether each subtype has its own job in the brain [2].

Three features set NMDA receptors apart from other glutamate receptors [1]:

• they need two molecules to bind before they open: glutamate and glycine (or D-serine);
• magnesium in the fluid outside the cell blocks the channel in a way that depends on the cell's voltage;
• they let calcium through readily.

Glutamate is released at the synapse with each signal, while glycine or D-serine is thought to be present at fairly constant levels [1].

Because glycine is one of the two molecules the receptor needs [1], research on glycine as a supplement can involve NMDA receptors.

These links are mechanisms. That a compound binds to, activates or blocks a receptor in a lab study says nothing, on its own, about sleep, memory or mood in people. On NootropicsWork, mechanism findings are labeled as such, and grades come only from outcomes measured in people.

• Receptor: the general idea behind the NMDA receptor.
• Glutamate and glycine: the two molecules that must bind before the channel opens.