Glossary
Glutamate
What is Glutamate?
Glutamate is the brain's main excitatory neurotransmitter: a chemical messenger that helps neurons communicate. It is involved in learning, memory, and changes in the strength of connections between neurons.
What are glutamatergic neurons?
Glutamatergic neurons use glutamate as a neurotransmitter. “Glutamatergic signaling” refers to communication involving glutamate; the term names the signaling system rather than a single behavior or mental process.
Functions of Glutamate
Excitatory Transmission
Fast excitatory effects occur mainly through ionotropic glutamate receptors, which control ion channels. Glutamate also acts through metabotropic receptors that modify cellular activity in other ways. The effect depends on the receptor and the circuit; “excitatory neurotransmitter” does not mean that every glutamate receptor always excites a neuron.
Neural Plasticity, Learning, and Memory
Glutamate signaling helps synapses strengthen or weaken in response to activity. These changes are part of neural plasticity, the brain's capacity to change with experience. Glutamate also participates in the development of neural connections and circuits.
Glutamate and Brain Disorders
Researchers study altered glutamate signaling in conditions including epilepsy, Alzheimer's disease, Parkinson's disease, and schizophrenia. Excessive excitation can be harmful, but these conditions are not interchangeable examples of “too much glutamate.” Receptor function, location, and timing matter.
One clinical example is memantine, which blocks NMDA-type glutamate receptor channels and is used to manage symptoms of moderate to severe Alzheimer's disease. Its use does not establish that it prevents the underlying neurodegeneration by reducing excitotoxicity.
The useful concept is regulated signaling within circuits. There is no single whole-brain glutamate number that defines good brain health.