Injection of the competitive NMDA receptor antagonist AP-5 into the nucleus accumbens of monoamine-depleted mice induces pronounced locomotor stimulation.

Following injection of 5 micrograms of the competitive NMDA receptor antagonist AP-5 into the nucleus accumbens of monoamine-depleted mice a pronounced locomotor stimulation was produced. Additional treatment with an intraperitoneal (i.p.) injection of the alpha-adrenoceptor agonist clonidine markedly increased the locomotor effects of AP-5 administration into the nucleus accumbens. Injection of 5 or 10 micrograms AP-5 into the dorsal striatum was ineffective with regard to locomotor stimulation. However, when AP-5 (10 micrograms) was combined with an i.p. injection of clonidine, a marked locomotor stimulation was produced following application into the dorsal striatum, but not following application into the prefrontal cortex. The present results are in line with the idea that corticostriatal glutamatergic pathways, especially those projecting to the ventral striatum, exert an inhibitory influence on psychomotor functions.