Memantine selectively depresses NMDA receptor-mediated responses of ratspinal neurones in vivo

The clinically used agent memantine (1-amino-3,5-dimethyladamantane) can act as an antagonist of NMDA (N-methyl-D-aspartate) when tested in vitro, but whether this applies with clinically relevant doses under in vivo conditions is not clear. In this study memantine has been compared with the known NMDA channel blocker ketamine, by intravenous administration in anaesthetized rats, for effects on the responses of spinal neurones both to iontophoretic administrations of excitatory amino acids and to peripheral noxious stimuli. Spontaneous activity, nociceptive responses and blood pressure were not significantly affected by memantine and ketamine, whereas both agents selectively reduced responses to NMDA.