NMDA receptors are brain receptors that are stimulated by glutamate. Poorly functioning NMDA receptors are thought to be involved in the pathology of schizophrenia. This hypothesis is based on the observation that PCP, which blocks the NMDA receptor, produces symptoms and cognitive impairments similar to schizophrenia. Efforts to enhance the function of the NMDA receptor with glycine and D-cycloserine have met with limited success. An alternative approach would be to use the drug acamprosate.