Spatial and temporal patterning distinguishes the locomotor activating effects of dizocilpine and phencyclidine in...

A behavioral pattern monitor was used to assess the effects of dizocilpine (MK-801) and phencyclidine on the spatial and temporal patterns of locomotion and investigatory behavior in rats. The monitor provided both quantitative measures of crossovers, rearings and holepokes and qualitative measurement of the spatial and temporal patterns of locomotion. Dizocilpine (0.004-0.5 mg/kg) and phencyclidine (0.25-5.0 mg/kg) produced similar, dose-dependent increases in locomotor activity. At small doses, dizocilpine and phencyclidine increased investigatory holepokes, while at larger doses, both drugs significantly decreased the number of holepokes. Rearings were reduced similarly by the larger doses of each drug. Both dizocilpine and phencyclidine produced perseverative spatial patterns of locomotion, especially at larger doses. However, the locomotor patterns produced by these drugs were found to be dissimilar in spatial quality. After phencyclidine, animals frequently circled the perimeter of the monitor chamber or moved repetitively in horseshoe or figure-8 patterns. By contrast, rats given dizocilpine completed small rotations about either end of the chamber. Pretreatment with a small dose (0.02 mg/kg) of haloperidol, prior to either dizocilpine (0.5 mg/kg) or phencyclidine (5.0 mg/kg) had no effect on the increase in locomotor activity or the decreases in investigatory holepokes produced by the drugs. However, haloperidol altered the effects of phencyclidine on the spatial and temporal patterns of locomotion, suggesting that sigma receptors or other haloperidol-sensitive binding sites, may influence the quality but not the quantity of phencyclidine-induced hyperactivity.