Effects of NMDA receptor blockers on cocaine-stimulated locomotor activityin mice

Effects of MK-801 and ketamine, N-methyl-D-aspartate (NMDA) receptor blocke rs, on cocaine-stimulated locomotor activity were investigated in male Swis s-Webster mice. MK-801 (0.25, 0.5, 1.0 and 2.5 mg/kg), ketamine (10, 25 and 50 mg/kg) or saline was injected 20 min before cocaine (5, 10 and 20 mg/kg i.p.). Locomotor activity was measured for 30 min immediately following co caine treatment. All doses of the drugs were also tested for ability to dep ress or stimulate locomotor activity in the naive (no cocaine-treated) mice . Cocaine produced a dose-dependent increase in locomotor activity that was blocked dose-dependently by MK-801 or ketamine. The blockade by MK-801 was more prominent than by ketamine. Our results may suggest that cocaine-indu ced locomotor stimulation in mice is modulated via NMDA receptor mediated m echanisms. (C) 2000 Elsevier Science B.V. All rights reserved.