title: Different receptor sites mediate opioid agonism and antagonism.
mesh_terms: D000818:Animals; D001665:Binding Sites; D007700:Kinetics; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D009292:Narcotic Antagonists; D009294:Narcotics; D011957:Receptors, Opioid; D009271:Naltrexone; C024524:beta-funaltrexamine