Phencyclidine-induced stereotyped behaviors after injection of ethylketocyclazocine, Mr 2266 and naltrexone in rats.

The effects of ethylketocyclazocine (EKC), Mr 2266 and naltrexone on the stereotyped behaviors induced by an intraperitoneal injection of phencyclidine (PCP) were examined. PCP-induced turning, backpedalling, head weaving and sniffing were antagonized by pretreatment with EKC (0.25-4.0 mg/kg). While pretreatment with Mr 2266 (2.5 mg/kg), a kappa selective antagonist, and naltrexone (10 mg/kg), a mu selective antagonist, failed to affect the PCP-induced stereotypy, Mr 2266 antagonized the suppressing effect of EKC on PCP-induced stereotypy. Taken into consideration, this suggests that kappa opioid agonists such as EKC antagonize PCP-induced stereotyped behaviors through a kappa opioid mechanism, and that the mu opioid receptor may not play an important role in the PCP-induced stereotypy in rats.