Acute effects of ketamine in the holeboard, the elevated-plus maze, and the social interaction test in Wistar rats.

Although noncompetitive NMDA receptor antagonists have shown an anxiolyticlike profile in several studies, such effects have not been observed consistently. Previous studies with ketamine, a noncompetitive NMDA antagonist, have employed only shock tests of anxiety based on conflict procedures. In the present experiment, the effect of an acute low dose of ketamine (7 mg/kg) was examined in adult male Wistar rats tested in three nonconflict tests: holeboard, social interaction, and elevated plus-maze paradigms. The results showed that ketamine decreased time spent in active social interaction and the number of rearings and central activity in the social interaction test. It also decreased the number of entries into the percentage of time spent in open arms and the total number of entries in the elevated plus-maze. No significant effect was observed in head dipping in the holeboard test, although the number of crossings did increase. These results suggest an anxiogeniclike effect of ketamine in contrast with results previously described for noncompetitive NMDA receptor antagonists. These effects of ketamine are more similar to those described for stimulant drugs such as caffeine, cocaine, or amphetamine in anxiety tests.