Definition
The formalin test refers to the quantification of characteristic nociceptive behaviors that occur in response to subcutaneous (s.c.) or intradermal injection of a dilute solution of formaldehyde in 0.9 % saline, typically into the dorsal or plantar hindpaw of rodents.
Characteristics
The formalin test was originally described by Dubuisson and Dennis (1977) using 50 μl of 5 % formalin injected s.c. into the dorsal surface of one forepaw in rats and cats. “Five percent formalin” consisted of 1 ml of saturated formaldehyde (37 %) in water + 19 ml 0.9 % saline (i.e., 1.85 % formaldehyde). It is now more common to inject between 0.2 % and 5 % formalin into the dorsal or plantar hindpaw, using 20–50 μl in rats or 10–25 μl in mice. Another common site is the lateral aspect of the muzzle, or the temporomandibular joint, in rats, as a model of orofacial pain (Clavelou et al. 1995). The hindpaw has replaced the forepaw...
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References
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Coderre, T.J., Abbott, F.V., Sawynok, J. (2013). Formalin Test. In: Gebhart, G.F., Schmidt, R.F. (eds) Encyclopedia of Pain. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-28753-4_1535
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DOI: https://doi.org/10.1007/978-3-642-28753-4_1535
Publisher Name: Springer, Berlin, Heidelberg
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