Antiaggressive effects of MPEP, a selective antagonist of mGlu5 receptors, in agonistic interactions between male mice.

mGlu5 receptors are highly concentrated in limbic brain structures involved in motivational and emotional behaviours. This study describes the effects of 2-methyl-6-(phenylethylnyl)pyridine (MPEP; 5, 10, 15, 20 and 25 mg/kg, ip), a selective antagonist of the mGlu5 receptors, on agonistic behaviour elicited by isolation in male mice. Individually housed mice were exposed to anosmic opponents in a neutral area 30 min after drug administration. Besides other behaviours, the aggressive (threat and attack) and exploratory behaviours were evaluated during 10 min using an ethologically based analysis. MPEP produced a behavioural profile characterized by a notable decrement of offensive behaviours, accompanied by a significant increase of exploratory behaviours (nonsocial exploration and social investigation). These findings suggest a role for mGlu5 receptors in aggression modulation.