Objective: Assessment of punctate mechanical allodynia and hyperalgesia using monofilaments of varying forces to measure withdrawal responses to touch stimuli
Materials & Equipment Checklist
8 items6 from ConductScience
Gather these items before starting the experiment. Check off items as you prepare.
Equipment3
Not specified • Not specified • Not specified • Not specified
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View Abstract
Rodents are commonly used to study the pathophysiological mechanisms of pain as studies in humans may be difficult to perform and ethically limited. As pain cannot be directly measured in rodents, many methods that quantify "pain-like" behaviors or nociception have been developed. These behavioral methods can be divided into stimulus-evoked or non-stimulus evoked (spontaneous) nociception, based on whether or not application of an external stimulus is used to elicit a withdrawal response. Stimulus-evoked methods, which include manual and electronic von Frey, Randall-Selitto and the Hargreaves test, were the first to be developed and continue to be in widespread use. However, concerns over the clinical translatability of stimulus-evoked nociception in recent years has led to the development and increasing implementation of non-stimulus evoked methods, such as grimace scales, burrowing, weight bearing and gait analysis. This review article provides an overview, as well as discussion of the advantages and disadvantages of the most commonly used behavioral methods of stimulus-evoked and non-stimulus-evoked nociception used in rodents.
Protocol Steps
1
Animal Placement
Place rodents individually in small cages with mesh or barred floor to allow access to hind paw
Not specifiedNot specified
Note: Cages must have penetrable bottom for monofilament application
View evidence from paper
“Rodents are placed individually in small cages with a mesh or otherwise penetrable bottom”
2
Monofilament Application
Apply monofilament perpendicularly to the plantar surface of the hind paw until it buckles, delivering constant pre-determined force
2–5 secondsNot specified
Von Frey Filaments
Matches: Von Frey Filaments - Force Range for Mice
Note: Force range: 0.2–13.7 mN for mice; 5.9–98 mN for rats. Alternative testing areas include dorsal surface of hind paw or abdomen
View evidence from paper
“A monofilament is applied perpendicularly to the plantar surface of the hind paw until it buckles, delivering a constant pre-determined force (typically 0.2–13.7 mN for mice and 5.9–98 mN for rats) for 2–5 s”
3
Response Assessment
Observe and record nocifensive behaviors including brisk paw withdrawal, licking, or shaking of the paw during or immediately after filament removal
Immediate observation during and after stimulusNot specified
Note: A positive response is defined as any nocifensive behavior exhibited during application or immediately after removal
View evidence from paper
“A response is considered positive if the animal exhibits any nocifensive behaviors, including brisk paw withdrawal, licking, or shaking of the paw, either during application of the stimulus or immediately after the filament is removed”
4
Up-Down Method (if using this approach)
Begin testing with a filament estimated to be close to the 50% withdrawal threshold. If no response, test next filament with higher force. Continue until mechanical force required to elicit paw withdrawal response in 50% of animals is determined
Not specifiedNot specified
Von Frey Filaments
Matches: Von Frey Filaments - Force Range for Mice
Note: This method is based on statistical formula used to determine LD50s. Alternative methods include ascending stimulus or percent response methods
View evidence from paper
“The 'up-down' Von Frey method is used to determine the mechanical force required to elicit a paw withdrawal response in 50% of animals, based on the statistical formula used to determine LD 50 s. The experiment begins by testing the response to a filament estimated to be close to the 50% withdrawal threshold. If there is no response, the next filament with a higher force is tes”
