Glutamate: NMDA Receptors

NMDA receptors are glutamate-activated ion channels with distinctive properties, including dependence on co-agonists and the electrical state of the receiving cell. They contribute to synaptic plasticity and the coordination of neural activity. Their role has attracted particular attention in schizophrenia research.

Glutamate is the brain’s principal excitatory neurotransmitter and is involved in learning, plasticity and communication across neural networks. It acts through several receptor types with different properties. Its normal role is essential, and a glutamate hypothesis of schizophrenia does not imply that ordinary dietary glutamate directly causes the illness.

Drugs that block NMDA receptors can produce experiences and cognitive changes resembling some features of psychosis, which supports investigation of NMDA-related mechanisms. This resemblance does not prove that schizophrenia is caused by the same pharmacological process. Receptor function may differ across cell types, including inhibitory interneurons. Attempts to modify this system have produced mixed clinical results. Explanations should distinguish experimental support for a hypothesis from an established treatment. There is no routine clinical NMDA test that identifies the cause of typical schizophrenia symptoms or determines an individual’s ideal intervention.

NMDA receptor opening normally depends on several conditions occurring together, making the receptor useful in activity-dependent changes at synapses. That complexity also means that simply describing it as underactive leaves important questions unanswered. Researchers need to identify the cell type, circuit and developmental stage involved before a mechanistic model can become a precise and effective treatment strategy.

Further reading: Research record 31299229.