The mGlu5 receptor agonist CHPG stimulates striatal glutamate release: possible involvement of A2A receptors.

The intrastriatal perfusion of the selective metabotropic glutamate (mGlu) 5 receptor agonist (RS)-2-chloro-5-hydroxy-phenylglycine (CHPG, 1000μM) significantly increased (∼+100%, p < 0.05) glutamate extracellular levels with respect to basal values. The potentiating effect of CHPG was prevented by the selective mGlu 5 receptor antagonist 2-methyl-6(phenyl-ethynyl)-pyridine (MPEP, 250 μM)) and by the adenosine A 2A receptor antagonist SCH 58261 (2mg/kg, i.p.). The results show that mGlu 5 receptors are involved in the regulation of striatal glutamate release and suggest an involvement of adenosine A 2A receptors in mGlu 5 receptor-mediated effects.