Effects of ketazocine, ethylketazocine and phenazocine on schedule-controlled behavior: antagonism by naloxone.
Dose-effect curves were determined for phenazocine (0.64-2.5 mg/kg), ketazocine (1.25-80 mg/kg) and ethylketazocine (1.25-80 mg/kg) in pigeons responding under a multiple fixed-ratio 30-response, fixed-interval 5-min schedule of grain presentation. All three opioid agonists decreased responding with the larger doses. The effects of phenazocine were completely antagonized by small doses of naloxone (0.01-1 mg/kg), whereas the effects of ethylketazocine required larger doses of naloxone (1-10 mg/kg) to be completely antagonized. The behavioral effects of ketazocine were partially attenuated by naloxone, but were not antagonized completely even by a 10 mg/kg dose of naloxone. These data from the pigeon are consistent with previous interpretations that the effects of phenazocine are mediated by actions at a mu opioid receptor, whereas the effects of ketazocine and ethylketazocine are mediated by actions at a kappa opioid receptor.
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D010856:Columbidae; D003213:Conditioning, Psychological / Q000187:drug effects*; D003496:Cyclazocine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D016314:Ethylketocyclazocine / Q000031:analogs & derivatives; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010620:Phenazocine / Q000494:pharmacology*
D000701:Analgesics, Opioid; D009270:Naloxone; D016314:Ethylketocyclazocine; C012395:ketazocine; D010620:Phenazocine; D003496:Cyclazocine