Behavioural profile of selective ligands for mGlu7 and mGlu8 glutamate receptors in agonistic encounters between mice

Evidence is accumulating for a role of glutamate transmission in aggression modulation. Recent studies indicate that glutamate metabotropic receptors (mGlu1 and mGlu5) are involved in the regulation of aggressive behaviour. However, to date, the possible role of mGlu7 and mGlu8 receptors has not been explored. In this work, we analyze the effect of acute administration of AMN082 (0.5-4 mg/kg, ip) and (S)-3,4-DCPG (2.5-10 mg/kg, ip), selective ligands for the mGlu7 and mGlu8 receptors, respectively, on agonistic encounters between male mice. Individually housed mice were exposed to anosmic opponents 60 or 30 min after drug administration. Ten min of dyadic interactions were staged between a singly housed and an anosmic mouse in a neutral area. The encounters were videotaped and the accumulated time allocated by subjects to ten broad behavioural categories was estimated using an ethologically based analysis. The highest dose of AMN082 (4 mg/kg) significantly reduced offensive behaviours (threat and attack), as compared with the control group, without depressing motility, whereas (S)-3,4-DCPG did not produce significant behavioural changes. Overall, these results suggest that mGlu7 receptors (but not mGlu8) may be implicated in the modulation of aggression.