Possible physiological control of morphine analgesia in mice

F. Cankat Tulunay, Min Feng Jen, Horace H. Loh

Research output: Contribution to journalArticlepeer-review


Several laboratories have reported that dynorphin and vasopressin may be present in the same neurons and released together in a fixed ratio. In this study, we report that vasopressin and dynorphin can regulate morphine-induced analgesia in the mouse tail-flick test. Its action is opposite that observed for dynorphin because, when administered simultaneously with morphine, vasopressin in a dose-related manner potentiated morphine-induced analgesia while dynorphin antagonized it. When vasopressin and dynorphin is administered together with morphine, morphine ED50 returned to control level.

Original languageEnglish (US)
Pages (from-to)317-319
Number of pages3
JournalEuropean Journal of Pharmacology
Issue number3-4
StatePublished - Sep 24 1982


  • Analgesia
  • Dynorphin
  • Morphine
  • Vasopressin


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