Place conditioning of mice with the NMDA receptor antagonists, eliprodil and dizocilpine.

Effects of noncompetitive and competitive NMDA receptor antagonists have been repeatedly characterized using place conditioning models. The present study aimed to characterize the effects in mice of another NMDA receptor antagonist acting at polyamine binding site, eliprodil. Five-day conditioning with eliprodil (1-30 mg/kg, i.p.) resulted in a dose-dependent avoidance of an eliprodil-paired compartment during post-conditioning tests. These effects were: (i) observed both with eliprodil and without drug, and (ii) less pronounced in individually housed mice subjected to repeated social defeats and mild footshocks prior to and during the conditioning period (compared to group-housed and individually housed nonstressed mice). In a parallel set of experiments, the effects of dizocilpine (MK-801; 0.03-0.3 mg/kg, i.p.) were evaluated using the same study design as for eliprodil. Conditioned place preference was established with the dizocilpine dose of 0.3 mg/kg and this effect was not affected by housing/stressing or drug exposures during the test.