title: Morphine analgesia: 2-way cross tolerance between systemic and intracerebral (periaqueductal gray) administrations.
mesh_terms: D000698:Analgesia; D000818:Animals; D002535:Cerebral Aqueduct / Q000187:drug effects; D002552:Cerebral Ventricles / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D007276:Injections, Intraventricular; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats
chemical_list: D009020:Morphine