Ketamine is a dissociative anesthetic and non-competitive NMDA antagonist. In addition to its use as an anesthetic, ketamine is also used as a research tool in modelling disorders such as schizophrenia. In at least one study, it was shown to activate the area of the prefrontal cortex linked to schizophrenia. It is also used as a model of the near-death experience.

Ketamine works by binding to and blocking glutamate receptors. It also inhibits reuptake of serotonin and noradrenalin, as well as activating serotonin metabolism and increasing subcortical release of dopamine.

Chemical structure:

     H   H
      \ /
    H--C
  H  H  \ H  O H   H
   \  \  \|  \\ \ /
    C--C  N   C--C   H
   //  \\  \ /    \ /
H-C      C--C      C
   \    /    \    / \
    C==C      C--C   H
   /    \    /|  |\
  H     Cl  H H  H H

Sources:
http://ams.cu.edu.tr/January1998Vol7No1/ketamine.htm
http://www.biopsychiatry.com/ketamine.htm