Role of Dopaminergic and Serotonergic Neuronal Systems in the Prefrontal Cortex of Rats in Phencycli-Dine-Induced Behaviors

This study was designed to determine the action sites of phencyclidine (PCP) involved in the development of behaviors such as head-weaving, immobility, turning and backpedalling in relation to dopaminergic and serotonergic neuronal functions. Injection of PCP into the caudate nucleus or prefrontal cortex dose-dependently produced head-weaving, although the injection of PCP into the nucleus accumbens failed to produce head-weaving. The intensity of head-weaving induced by injection of PCP into the prefrontal cortex was relatively high when compared to that induced by injection of PCP into the caudate nucleus or lateral ventricle. Pretreatment with p -chlorophenylalanine (300 mg/kg), a serotonin (5-HT) synthesis inhibitor, attenuated head-weaving induced by injection of PCP into the prefrontal cortex. Injection of PCP (50—100 μ g) into the prefrontal cortex also produced immobility for 5 min post-injection. Rats pretreated with pimozide (1 mg/kg), a dopamine (DA) antagonist, also produced immobility after the injection of PCP into the prefrontal cortex and this effect was attenuated by pretreatment with ritanserin, a 5 -HT₂ receptor antagonist. on the other hand, pretreatment with methamphetamine attenuated PCP (5 and 7.5 mg/kg)-induced turning and backpedalling but not head-weaving. Pretreatment with large doses of apomorphine, a DA agonist, also greatly attenuated PCP (7.5 mg/kg)-induced behaviors, i.e. head-weaving, turning and backpedalling. These effects of DA agonists were prevented by haloperidol (0.25 mg/kg), a DA antagonist. These results suggest that PCP-induced turning and backpedalling may be mediated by reducing dopaminergic transmission, although PCP-induced head-weaving and immobility may be produced by increasing serotonergic transmission in the prefrontal cortex.