Glutamate is the primary excitatory neurotransmitter of the human nervous system. It is an amino acid neurotransmitter that interacts with both ionotropic and metabotropic receptors. There are 3 identified ionotropic glutamate receptors: NMDA, AMPA, and kainate receptors, and 3 identified metabotropic glutamate receptors. Glutamate is removed from the synaptic cleft by excitatory amino acid transporters, or EAATs. Glutamate that is transported into glial cells is converted to glutamine before being sent back to the neuron to be converted back to glutamate, a process referred to as the glutamate-glutamine cycle.