Evaluation of brain pharmacokinetics of (+)MK-801 in relation to behaviour.

The non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist (+)MK-801 is widely used in animal research (over 3000 publications), however its extracellular brain concentration has never been reported. Here, we show using in vivo microdialysis that systemic injection of (+)MK-801 at doses of 0.05, 0.1 or 0.2mg/kg resulted in peak brain ECF concentration of 6, 14 or 34 nM, respectively. Moreover, (+)MK-801 resulted in a dose-dependent learning impairment in the Morris water maze as well as hyperactivity in the open field. These data demonstrate for the first time that (+)MK-801 at doses producing behavioural alterations expected from NMDA receptor blockade reaches extracellular brain concentrations corresponding to the affinity at NMDA receptors.