Effect of NMDA receptor antagonists on D1, D2 and D1/D2 mediated behaviors in intact rats

The effect of treatment with the competitive (CGP 43487) and non-competitive (MK-801) NMDA antagonists on behaviors induced by the stimulation of D1 (SKF 38393 induced grooming), D2 (LY 171555 elicited hypermotility) or D1/D2 (apomorphine induced locomotion and stereotypies) was observed in intact rats. The administration of low doses of MK-801 (0.03 and 0.06 mg/kg) or CGP 43487 (0.375 and 0.75 mg/kg), which were without effect by themselves on animal locomotion, reduced the hyperactivity induced by LY 171555 (0.15 mg/kg) and did not change the stimulating motor effect of a low dose of apomorphine (0.15 mg/kg). Spontaneous grooming behavior was inhibited by both NMDA antagonists, whereas the administration of CGP 43487 but not of MK-801 potentiated grooming response to SKF 38393 (10 mg/kg). Both antagonists increased stereotyped behavior induced by 0.25 mg/kg apomorphine. The results, according to those obtained by other authors in DA depleted/lesioned animals, support the view of interaction between NMDA/D1,D2 receptors in intact rats.