Effects of the NMDA/glycine receptor antagonist, L-701,324, on morphine- and cocaine-induced place preference.

Effects of the novel NMDA/glycine receptor antagonist, L-701,324, on morphine- and cocaine-induced conditioned place preference (CPP) were examined in male Wistar rats. After determination of initial preference, animals were conditioned with morphine (5 mg/kg, i.p.) or cocaine (5 mg/kg, i.p.) for 3 conditioning trials, alone or in combination of these drugs with L-701,324 (2.5 mg/kg and 5 mg/kg, p.o.). L-701,324 prevented acquisition of the place preference produced by morphine and cocaine. Administration of L-701,324 on the test day attenuated the expression of morphine-induced CPP, whereas it had no effect on cocaine CPP. When L-701,324 was given alone it did not affect dependent variables (i.e. time spent in non-preferred compartment) suggesting that L-701,324 did not display any reinforcing properties by itself. Our current data suggest that glycine site on the NMDA receptor complex may be involved in the mediation of the rewarding effects of drugs of abuse.