– 1-Aminocyclopropane-1-carboxylic acid (ACC) is an intermediate in the synthesis of ethylene, the plant hormone responsible for biological processes ranging from seed germination to organ senescence. It is a small molecule agonist at the glycine modulatory site of the NMDA receptor (EC50 = 0.7-0.9 μM) in the presence of low levels (1 μM) of glutamate and as a competitive antagonist at the glutamate-binding site on NMDA receptors (EC50 = 81.6 nM) with high levels (10 μM) of glutamate.2 This compound has been reported to protect against neuron cell death in vivo models of ischemia by enabling moderate levels of NMDA receptor activation and attenuating any excess NMDA receptor signaling that may lead to neurotoxicity.