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mammalian CNS, the actions of which are regulated by ionotropic glutamate (iGlu) and metabotropic glutamate receptors (mGlu). mGlu receptors are a family of G-protein-coupled receptors comprising eight members, refered to as mGlu1-8. Group I receptors include mGlu1 and mGlu5, which when expressed are coupled via Gq to phospholipase C. Group II (mGlu2 and mGlu3) and group III (mGlu4,6,7,8) receptors are coupled to Gi and inhibit cAMP formation when expressed in cell lines (Ferraguti & Shigemoto, 2006). Glutamate is involved in the regulation of aggressive behaviour. In this sense, studies of ionotropic receptors (NMDA and AMPA) show that glutamate neurotransmission could play a role in aggression. In relation to the NMDA receptors, the existing results are equivocal. For instance, phencyclidine (PCP) was found both to facilitate fighting (Wilmot, Vanderwende, & Spoerlein, 1987) and to decrease the number of attacks by resident mice toward intruders (Miczek & Haney, 1994). Similarly, the PCP-like NMDA receptor antagonist dizocilpine increased aggressiveness in a study by McAllister (1990), whereas suppressed aggression induced by a challenge dose of apomorphine (Lang et al., 1995). By contrast, the involvement of AMPA-type glutamate receptors in the regulation of social behaviour has been clearly suggested by experiments with mice deficient for the GluR-A subunit-containing AMPA receptors showing reduced intermale aggression. Thus, of the AMPA family of glutamate receptors, knock-out mice lacking the Behavioural profile of selective ligands for mGlu7 and mGlu8 glutamate receptors in agonistic encounters between mice