NMDA agonists and antagonists as probes of glutamatergic dysfunction and pharmacotherapies in neuropsychiatric disorders.

Antagonists of the N-methyl-D-aspartate (NMDA) subclass of glutamate receptors and agonists of the glycine-B coagonist site of these receptors have been important tools for characterizing the contributions of NMDA receptor pathophysiology to a large number of neuropsychiatric conditions and for treating these conditions. Among these disorders are Alzheimer's disease, chronic pain syndromes, epilepsy, schizophrenia, Parkinson's disease, Huntington's disease, addiction disorders, major depression, and anxiety disorders. This review will examine pathophysiological and therapeutic hypotheses generated or supported by clinical studies employing NMDA antagonists and glycine-B agonists and partial agonists. It will also consider ethical issues related to human psychopharmacological studies employing glutamatergic probes.