Behavioural effects of NMDA-receptor antagonists.

NMDA receptor-antagonists were tested in dose ranges that have previously been found to produce anticonvulsant and anticataleptic (antiparkinsonian) effects in rats. Non-competitive NMDA receptor-antagonists had strong psychomotor stimulating effects, the competitive ones were weaker in this respect when given systemically. However, when locally injected into the striatum or into the nucleus accumbens, also the competitive NMDA-antagonists induced psychomotor stimulation. If at all, NMDA receptor-antagonists have rewarding effects, then they seem to be elicited only by the non-competitive NMDA receptor-antagonists. In maze tests, sensitive for hippocampally mediated learning, NMDA receptor-antagonists impaired learning. While non-competitive NMDA-antagonists produced learning deficits over the whole dose range tested, competitive ones were only effective at higher dose levels.