Fig. (2).

Subcellular localization of the different mGluR subtypes in the glutamatergic synapse. Group I mGluRs, including mGluR1 and mGluR5, are almost exclusively located post-synaptically, and mGluR5 are present both synaptically and extrasynaptically. Group II mGluRs are predominantly located on presynaptic terminals in the extrasynaptic space, with the exception of mGluR3 which is highly expressed on glial cells as well as postsynaptically. Group III mGluRs are also principally expressed presynaptically; interestingly, mGluR7 is located in the synaptic cleft while mGluR4 and 8 are mostly extrasynaptic.

Note that mGluR3 and mGluR7 are also present on non-glutamatergic (e.g. GABAergic) terminals.