EFFECTS OF DIZOCILPINE (MK-801) ON MOTOR-ACTIVITY AND MEMORY

The effects of MK-801 upon motor activity and memory were assessed in a novel use of open-field behavior testing. In this study, rats were t reated with different doses of MK-801 (0.025, 0.05, 0.1 and 0.2 mg/kg) and given a brief 10-min exposure to an open-field in which locomotor activity and within-session habituation were measured. Doses of MK-80 1 less than or equal to 0.1 mg/kg had no effect upon locomotor activit y or within-session habituation. MK-801 0.2 mg/kg produced a marked hy perlocomotion and completely prevented within-session habituation. One day later, the animals were tested for their retention of habituation to evaluate the effects of MK-801 on memory processes. In that animal s treated with 0.2 mg/kg MK-801 failed to habituate to the novel envir onment under the influence of 0.2 mg/kg MK-801, it was not surprising that these animals were impaired on the retention test for the novel e nvironment. Importantly, however, the 0.1mg/kg MK-801 treatment, which did not affect locomotor activity or within-session habitation to the novel environment, severely interfered with retention of the novel en vironment. Additional experiments indicated that this result could not be accounted for by drug conditioning or drug state-dependent effects . Thus, the results indicated that MK-801 can produce profound effects upon motor activity and memory and that these two effects can be disa ssociated.