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. In human patients, mutations in the
GRM6 gene are associated with
congenital stationary night blindness. ==See also==