n. a salt or ester of the amino acid glutamic acid that serves as the predominant excitatory neurotransmitter in the brain. Glutamate plays a critical role in cognitive, motor, and sensory functions. It exerts its effects by binding to glutamate receptors on neurons. Excessive activity of glutamate at these receptors is associated with damage to nerve tissue (neurotoxicity) and cell death (see excitotoxicity), possibly the result of calcium ions flooding into the cell following overstimulation of NMDA receptors.