Phencyclidine-induced dopamine-dependent behaviors in chronic haloperidol-treated rats.

This study was designed to assess whether phencyclidine (PCP) produces dopamine (DA)-dependent behaviors such as licking, biting and gnawing at low doses after withdrawal from chronic haloperidol (HAL) treatment in rats. Low doses of PCP (2.5 and 5 mg/kg) produced licking, gnawing, biting and self-biting in rats after withdrawal from chronic HAL treatment, which were not observed in the vehicle-pretreated rats given PCP at the same dose range. These behaviors were similar to DA-dependent behaviors produced by methamphetamine and apomorphine in rats after withdrawal from chronic HAL treatment. The PCP-induced behaviors were attenuated by acute pretreatment of DA antagonist, HAL (0.25 mg/kg, IP). Furthermore, at doses of 5 or 7.5 mg/kg, PCP-induced head weaving and backpedalling, which were mediated by both DA and serotonin (5-HT) neurons, significantly increased in rats after withdrawal from chronic HAL-treatment. These results suggest that dopaminergic systems play an important role for PCP-induced behavioral responses.