The interaction between MK-801 and receptors for N-methyl-D-aspartate: functional consequences.

Electrophysiological studies using a cortical slice preparation revealed that MK-801 is a potent, non-competitive, antagonist of N-methyl-D-aspartate (NMDA)-induced depolarisations. Also, MK-801 was a highly selective antagonist, exhibiting a high degree of use-dependency. It completely blocked responses to NMDA and quinolinic acid but had no effect on responses produced by kainic acid or quisqualic acid. Using [3H]MK-801, high affinity binding sites for MK-801 were detected in membranes of the rat brain. The pharmacological specificity and regional distribution of binding sites for MK-801 were consistent with an action of the compound at the level of the NMDA receptor-associated ion channel. Administered parenterally, MK-801 had a remarkable neuroprotective role. It caused essentially complete protection against loss of neurones produced by injection of neurotoxic doses of NMDA or quinolinic acid into the striatum or hippocampus. Furthermore, MK-801 was highly effective in preventing loss of hippocampal neurones following bilateral occlusion of the common carotid arteries in the gerbil.