Respiratory and circulatory effects of centrally administered phencyclidine in anesthetized dogs

1. Anesthetized dogs were given phencyclidine HCl (PCP) by intracerebroventricular (i.c.v.) injection. 2. Physiological parameters were monitored after consecutive doses of 0.5, 1.0 and 2.0 mg of PCP. 3. Dose-related changes seen, including bradycardia, hypotension and bradypnea, were opposite to those produced by i.v. doses. 4. Single doses of 1.0 or 2.0 mg of PCP confirmed the prior observations, and the latter provided the baseline for further observations on dogs receiving PCP before various i.c.v. pretreatments--atropine, haloperidol, phentolamine or propranolol--in efforts to characterize the central neurotransmitter system(s) involved in the PCP effects.