The effects of MK801 on place conditioning.

The appetitive properties of MK801 were investigated using the conditioned place preference paradigm. Male Sprague-Dawley rats received conditioned place preference training for a four-day period. The conditioning box consisted of three chambers with distinctive visual and tactile cues, separated by removable doors. On alternating days rats received MK801 (0.05, 0.1, 0.25, 0.5 and 0.75 mg/kg) paired with one side of the chamber and saline paired with the other side. On the fifth day, rats were placed in the center chamber and the time spent in each chamber, as well as entries into each chamber were recorded by a trained observer. MK801 produced a conditioned place preference for side paired with drug for the four highest doses. Contrary to previous findings, these results indicate that MK801 is appetitive at doses higher than has previously been assumed.