Thermal, mechanical and chemical peripheral sensation in amphibians: Opioid and adrenergic effects

Stan Willenbring, Craig W. Stevens

Research output: Contribution to journalArticle

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The acetic acid test (AAT) is a quantifiable assay of the response to noxious chemical stimuli on the hindlimb of the northern grass frog, Rana pipiens. AAT is sensitive to both opioid and adrenergic agonist modulation. The present study introduces the novel use of mechanical and thermal stimulus behavioral assays in comparison with the established acetic acid test in studying nociception in frogs. We evaluated mechanical and thermal responses and their sensitivity to systemic morphine (MOR) or dexmedetomidine (DEX) administrations with comparison to AAT. MOR produced dose-related elevations of response thresholds in all three sensory tests, whereas DEX produced elevations in the thermal and AAT assays but had no effect on sensitivity to non-noxious mechanical stimuli. The results suggest a distinct separation of sensory modalities in the frog similar to that observed in mammals and indicate the usefulness of this amphibian model in further studies of nociception.

Original languageEnglish
Pages (from-to)125-133
Number of pages9
JournalLife Sciences
Issue number2
Publication statusPublished - 1 Dec 1995



  • amphibian pain model
  • chemical sensitivity
  • dexmedetomidine
  • mechanical sensitivity
  • morphine
  • thermal sensitivity

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