2-Amino-5-Phosphonopentanoic Acid (AP5)

AP5 is a selective NMDA receptor antagonist that competitively inhibits the ligand (glutamate) binding site of NMDA receptors. AP5 blocks the cellular analog of classical conditioning in the sea slug Aplysia californica, and has similar effects on Aplysia long-term potentiation, since NMDA receptors are required for both. It is sometimes used in conjunction with the calcium chelator BAPTA to determine whether NMDARs are required for a particular cellular process. In general, AP5 is very fast-acting within in vitro preparations, and can block NMDA receptor action at a reasonably small concentration. The active isomer of AP5 is considered to be the D configuration, although many preparations are available as a racemic mixture of D- and L-isomers. AP5 was developed by Jeff Watkins and Harry Olverman. AP5 can block the conversion of a silent synapse to an active one, since this conversion is NMDA receptor-dependent.