Methodological refinements to the mouse paw formalin test. An animal model of tonic pain

Christopher W. Murray, Frank Porreca, Alan Cowan

Research output: Contribution to journalArticlepeer-review

188 Scopus citations


The formalin tonic pain test has recently been adapted for use in mice. We have observed two problems with this procedure. First, compared to a vehicle control group, the majority of mice injected in a hind paw with dilute formalin exhibited a significant nociceptive response (paw licking), including peaks of activity, well beyond the end of the recommended observation period; and, second, an unacceptably wide variation in response occurred. We report two modifications that eliminate these difficulties: a) extending the observation period to 20-45 min postformalin injection, and b) lightly anesthetizing the mice with ether before injection of formalin into the paw. The modified protocol was tested by evaluating morphine, pentazocine and zomepirac (analgesic A50 values were 2.1, 23.8, and > 100 mg/kg, s.c., respectively). An intrathecal or intracerebroventricular injection of saline, given to the lightly anesthetized mouse, did not interfere with the nociceptive behavior; this finding widens the applicability and usefulness of the test. Collectively, these refinements significantly improve the mouse formalin model of tonic pain.

Original languageEnglish (US)
Pages (from-to)175-186
Number of pages12
JournalJournal of Pharmacological Methods
Issue number2
StatePublished - Sep 1988


  • Analgesia
  • Analgesic testing
  • Chronic pain
  • Formalin test
  • Nociception
  • Tonic pain

ASJC Scopus subject areas

  • Pharmacology


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