GRM2 and Parkinson disease: This might because the beneficial effects of locomotor observed in PD models after systemic administration of mGlu2/3 agonists could derive from the reduction of both corticostriatal transmission and subthalamic nucleus hyperactivity (Rouse et al., 2000; Murray et al., 2002) and the content of dopamine in striatum might not influence its antiparkinsonian properties (Konieczny et al., 1998; Ali and Salter, 2001).