L-glutamate is the major excitatory neurotransmitter in the central nervous system and activates both ionotropic and;metabotropic glutamate receptors. 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 on the basis of sequence homology, putative signal;transduction mechanisms, and pharmacologic properties. Group I includes GRM1 and GRM5 and these receptors have been;shown to activate phospholipase C. Group II includes GRM2 and GRM3 while Group III includes GRM4, GRM6, GRM7 and GRM8.;Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist;selectivities. Two transcript variants encoding different isoforms have been found for this gene.