title: Morphine antinociception: evidence for the release of endogenous substance(s).
mesh_terms: D000818:Animals; D002946:Cisterna Magna / Q000502:physiology; D004388:Dura Mater / Q000502:physiology; D008026:Ligation; D008297:Male; D051379:Mice; D009020:Morphine / Q000627:therapeutic use*; D010146:Pain; D013116:Spinal Cord / Q000502:physiology*
chemical_list: D009020:Morphine