L glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamatergic neurotransmission is involved in most aspects of normal brain function and can be perturbed in many neuropathologic conditions. The metabotropic glutamate receptors are a family of G protein-coupled receptors that have been divided into 3 groups. Group III receptors include GRM7 and are linked to the inhibition of the cyclic AMP cascade. GRM7 has been reported to be expressed in active zones of presynaptic axon terminals in various regions of the brain, eye, and spinal cord.