To know about Ketamine mechanism of action we need to know that Ketamine is a non-competitive antagonist to the phencyclidine site of N-methyl-d-aspartate (NMDA) receptor for glutamate, though Ketamine mechanism of action has effects that are mediated by interaction with many others receptors.
N-Methyl-D-Aspartate Receptor Antagonism : NMDA receptors are ligand-gated ion channels that are permeable to Ca and to Na and K to some extent. The channel activation requires binding of the excitatory neurotransmitter, glutamate with glycine as an obligatory coagonist. Conventional NMDA receptors consist of two subunits (NRI and NR2A-D), and more rarely NR3A or B subunits.
There are binding sites for glutamate, the endogenous agonist, and glycine. Ketamine mechanism of action binds to the phencyclidine receptor of the NMDA channel noncompetitively and thus, inhibits activation of NMDA receptors by glutamate.
This interaction with phencyclidine binding sites appears to be stereoselective, with the S (+) isomer of ketamine having three to fourfold greater affinity than R (-) isomer reflecting its greater analgesic and anaesthetic potencies.