* (+)MK-801 (1 mg/kg i.p.) or saline was given 30 min before the administration of MPTP (40 mg/kg s.c.), and the animals were killed at 1.5 hr after MPTP. ** Two injections of (+)MK-801 were given at 4-hr intervals; MPTP was administered 30 min after the first injection, and the mice were killed at 8 hr after the MPTP. Data represent means ± S.E.M. ^† Statistically different (P < .001) as compared with the value obtained with MPTP alone.