title: Tolerance of high doses of morphine: lack of evidence of learning.
mesh_terms: D000818:Animals; D001245:Association Learning; D003216:Conditioning, Operant; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D004777:Environment; D005108:Extinction, Psychological; D007858:Learning; D007928:Lethal Dose 50; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D012931:Social Environment
chemical_list: D009020:Morphine