Activation of group III mGluRs produces antiparkinsonian actions in both acute and chronic rodent models of PD. A, Effects of vehicle (PBS, intracerebroventricular) and increasing doses of l-AP4 (5, 50, and 100 nmol, i.c.v.) on haloperidol-treated rats (n = 4-7 animals per group). Catalepsy was measured using a rectangular vertical grid. **p < 0.01 compared with vehicle group. B, Effects of l-AP4 (50 nmol, i.c.v.) and vehicle (PBS, intracerebroventricular) on reserpine-treated rats (n = 4-7 animals per group). *p < 0.05 compared with vehicle group. C, Effects of l-AP4 (100 nmol, i.c.v.) and l-DOPA (6 mg/kg, i.p.) on forelimb asymmetry in unilateral 6-OHDA-lesioned rats (n = 4 animals per group). Asymmetry score = [% ipsilateral paw - (% contralateral paw + % both paws)]. Positive asymmetry scores reflect preferential use of the forelimb ipsilateral to the lesion site. Negative asymmetry scores, or scores approaching zero, reflect a lack of ipsilateral bias relative to the use of the contralateral forelimb or simultaneous use of both forelimbs. *p < 0.05 (l-AP4); **p < 0.01 (l-DOPA), compared with corresponding pretreatment groups.