title: Tryptophan reversal of tolerance to analgesia induced by central grey stimulation.
mesh_terms: D000328:Adult; D000698:Analgesia; D002986:Clinical Trials as Topic; D003061:Codeine / Q000008:administration & dosage / Q000627:therapeutic use; D004311:Double-Blind Method; D004361:Drug Tolerance; D004599:Electric Stimulation Therapy; D005260:Female; D006801:Humans; D008297:Male; D008636:Mesencephalon / Q000187:drug effects*; D008875:Middle Aged; D010148:Intractable Pain / Q000628:therapy*; D010919:Placebos; D014364:Tryptophan / Q000627:therapeutic use*
chemical_list: D010919:Placebos; D014364:Tryptophan; D003061:Codeine