title: Conditioned fear enhances morphine analgesia in the rat.
mesh_terms: D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology; D005239:Fear / Q000502:physiology*; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000523:psychology*; D051381:Rats; D011930:Reaction Time / Q000187:drug effects
chemical_list: D009020:Morphine