N-methyl-D-aspartate receptor agonists and antagonists partially affect the duration of ketamine anesthesia in the rat.

The effects of intracerebroventricular injection of excitatory amino acids which act on the N-Methyl-D-aspartate (NMDA) receptor complex on the duration of loss of righting reflex (DLRR) induced by intravenous injection to ketamine (20 mg/kg) were investigated in rats. Ketamine-induced DLRR was 10.3 min, but NMDA receptor agonistsD-alanine (200 μg) or NMDA (0.15 μg) did not change DLRR. However,D-alanine combined with NMDA significantly shortened DLRR (7.7 min). The NMDA receptor antagonist 7-chlorokynurenic acid (10 μg) alone prolonged DLRR significantly (16.2 min), but not when combined withD-alanine. These data suggest that NMDA receptor blockade contributes at least partially to the mechanism of ketamine anesthesia.