Acute and chronic phencyclidine effects on locomotor activity, stereotypy and ataxia in rats

Behavioral rating scales, developed to measure phencyclidine (PCP)-induced stereotypy and ataxia in rats, were tested using acute dose-response and chronic paradigms with concomitant assessment of locomotor activity by automated counters. Also, effects of chronic PCP on apomorphine-induced stereotypy were assessed as a test of dopamine supersensitivity. A linear dose-response effect was found for measures of all three behaviors through moderate dose levels (2-6 mg/kg), but only ataxia ratings continued to increase, showing a linear relationship through the higher (8 and 10 mg/kg) doses. Chronic daily PCP administration showed progressive augmentation of stereotypy, tolerance to ataxia at 10 min post-injection, and a biphasic increase followed by decrease to day 1 levels in locomotor activity over 14 days. No significant change was found in apomorphine stereotypy following chronic PCP treatment. The chronic behavioral changes demonstrated in this study may provide a model of PCP-induced psychological and cognitive changes seen following chronic usage in man.