Behavioral effects of morphine, levorphanol, dextrorphan and naloxone in the frog Rana pipiens

Paul D. Pezalla, Craig W. Stevens

Research output: Contribution to journalArticle

39 Scopus citations


Systemic morphine induces explosive motor behavior and generalized muscular rigidity in frogs. Naloxone does not reverse either of these effects of morphine but at high doses causes muscular flaccidity and unresponsiveness to stimulation. Intraspinal morphine induces rigidity, but not explosive motor behavior, and this action is blocked by naloxone. Behavioral effects are seen rarely after intraspinal levorphanol (rigidity) and never after intraspinal dextrorphan or naloxone. In contrast to systemic morphine and naloxone, systemic levorphanol and dextrorphan are lethal to frogs at high doses.

Original languageEnglish
Pages (from-to)213-217
Number of pages5
JournalPharmacology, Biochemistry and Behavior
Issue number2
Publication statusPublished - Aug 1984



  • Amphibians
  • Dextrorphan
  • Levorphanol
  • Morphine
  • Naloxone
  • Opiates
  • Rana pipiens

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