Subchronic phencyclidine in rats: alterations in locomotor activity, maze performance, and GABA(A) receptor binding.

Phencyclidine (PCP), an antagonist at the N-methyl-D-aspartate subtype of ionotropic glutamatergic receptors, decreases gamma-aminobutyric acid (GABA)ergic inhibition, suggesting that changes in GABAergic receptor function underlie behavioral and cognitive deficits resulting from repeated administration of PCP. To test this hypothesis, male Sprague-Dawley rats treated with PCP (4.5 mg/kg, intraperitoneal, twice a day for 7 consecutive days) or saline were tested in behavioral and cognitive tasks 7 days after injections. The PCP group showed increased amphetamine (1.5 mg/kg)-stimulated locomotor activity, and exhibited a greater number of errors in the double Y-maze memory task, when compared with controls. Subchronic PCP treatment increased [H]muscimol-binding sites and decreased affinity for [H]muscimol binding in frontal cortex, hippocampus, and striatum in comparison with controls. There were no changes in the expression of glutamic acid decarboxylase or the GABA membrane transporter protein. These data show that subchronic PCP administration induces an impaired performance of a previously learned task and an enhanced response to amphetamine in the rat. The observed changes in GABAA receptors in the rat brain are consistent with the notion that alterations in GABAergic receptor function contribute to the behavioral and cognitive impairments associated with repeated exposure to PCP.