Glutamate is the principal excitatory neurotransmitter in the central nervous system. It operates through two main classes of receptors: ionotropic receptors (iGluRs), which are ligand-gated ion channels, and metabotropic receptors (mGluRs), which couple to G-proteins to modulate cellular responses via ion channels or intracellular second messengers.mGluR6 belongs to the third group of metabotrophic glutamate receptors. Its expression in the central nervous system is restricted to retinal rod bipolar cells, and it’s localized to their postsynaptic dendritic membranes. In the peripheral nervous system, it is also detected in bone marrow stromal cells. mGluR6 inhibits adenylate cyclase, and was shown to inhibit Ca2+ influx and nitric oxide synthase activity.