title: Analysis of reinforcement during intragastric self-administration of morphine and methadone in the rat.
mesh_terms: D000818:Animals; D006801:Humans; D007440:Intubation; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000494:pharmacology*; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology; D051381:Rats; D012054:Reinforcement, Psychology; D012646:Self Administration
chemical_list: D009020:Morphine; D008691:Methadone