Involvement of opioid receptors in hypo- and hyperthermic effects induced by phencyclidine in mice

Experiments were conducted in order to examine the mechanism of changes in body temperature induced by phencyclidine (PCP) in mice. It is well known that morphine changes body temperature in a biphasic manner. PCP also produced hyperthermia at low doses (5 and 10 mg/kg) and hypothermia at high dose (40 mg/kg). The changes in body temperature induced by PCP were blocked by naloxone, a mu antagonist. Pretreatment with morphine (2.5 mg/kg), a mu agonist, or ethylketocyclazocine (EKC: 2.5 mg/kg), a kappa agonist, potentiated hypothermia induced by high dose of PCP. Effects of morphine and EKC on PCP-induced hypothermia were antagonized by naloxone. N-Allylnormetazocine (SKF 10 047: 20 mg/kg), a kappa and mu antagonist, antagonized PCP- and EKC + PCP-induced hypothermia but not morphine + PCP-induced hypothermia. Furthermore, Mr 2266, a kappa antagonist, antagonized PCP (10mg/kg)-induced hyperthermia and EKC + PCP-induced hypothermia. It is suggested that PCP may affect thermoregulation through mu and/or kappa opioid receptor mechanisms.