Effects of phencyclidine (PCP) on cardiorespiratory functions in the rhesus monkey

Effects of acute and chronic administration of phencyclidine (PCP) on heart rate (HR) and respiratory rate (RR) were studied in rhesus monkeys. Acute administration of PCP (2.0 and 4.0 mg/kg i.v.) produced decrements in both HR and RR within 15 to 30 min after drug administration. Simultaneously, with this cardiorespiratory slowing, EEG tracings evidenced High-Voltage Slow-Waves (HVSW) and delta-waves. As HR and RR began to recover, High-Voltage Fast-Waves (HVFW) along with theta-waves developed in EEG recordings and persisted for 2-6 h, while both HR and RR were gradually returning to their respective pre-drug control levels. The intensity and duration of these PCP-induced effects were directly related to dosage level. Following chronic administration of PCP (daily dose of 2.0 or 4.0 mg/kg i.v.), its ability to produce cardiorespiratory alterations was significantly diminished along with a decrease in PCP-induced depression of EEG and behavioral activities. These results suggest that chronic PCP administration produces a tolerance to its depressant effect on HR, RR, EEG and behavioral activities in rhesus monkeys.