Notes: D-AP5 is a selective N-methyl-D-aspartate (NMDA) receptor antagonist (Kd = 1.4 μM) that competitively inhibits the glutamate binding site of NMDA receptors.{22827} Whereas D-AP5 is the active (−)-stereoisomer, its (+)-isomer (L-AP5) demonstrates considerably less potent NMDA receptor antagonist activity.{22827} AP5 has been widely used to study the activity of NMDA receptors particularly in regard to researching synaptic plasticity, learning, and memory.{22826}