Grimace Scale
Objective: Evaluation of spontaneous pain-like behaviors through assessment of facial expressions as a non-stimulus evoked nociception measure in rodents
Gather these items before starting the experiment. Check off items as you prepare.
Equipment3
Software1
TopCat Metrology • Not specified
1 item available from ConductScience
Estimated: $3,190.00
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Protocol Steps
Animal placement and acclimation
Place rodents individually in small cages with mesh or barred floor for testing
Note: Animals must be non-anesthetized for behavioral assessment
View evidence from paper
“Rodents are placed individually in small cages with a mesh or barred floor.”
Manual Von Frey monofilament application
Apply monofilament perpendicularly to the plantar surface of the hind paw until it buckles, delivering constant pre-determined force
Note: Force range: 0.2-13.7 mN for mice and 5.9-98 mN for rats. Plantar surface of hind paw is most commonly used, but dorsal surface or abdomen can also be tested.
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”
Assess nocifensive response
Observe and record animal response to monofilament application, including brisk paw withdrawal, licking, or shaking of the paw
Note: Response is considered positive if animal exhibits nocifensive behaviors either during application or immediately after filament 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.”
Electronic von Frey testing (alternative method)
Apply single un-bending filament perpendicularly to hind paw and increase force by rotation of handheld device until paw withdrawal occurs
Note: Force ramp and paw withdrawal force are automatically displayed by software post-test
View evidence from paper
“A single, un-bending filament is applied perpendicularly to the hind paw. The force is increased by rotation of the handheld device until paw withdrawal occurs. The force ramp and paw withdrawal force are displayed by the software post-test.”
Randall-Selitto pressure test (alternative method)
Restrain rodent and place hind paw or tail between pointed probe tip and flat surface, increasing pressure until withdrawal or vocalization occurs
Note: Measures response to pressure stimulation as alternative to mechanical filament testing
View evidence from paper
“The rodent is restrained and the hind paw (or tail) is placed between a pointed probe tip and flat surface. The pressure is increased until withdrawal or vocalization occurs.”
Determine mechanical threshold using up-down method
Use up-down Von Frey method to determine mechanical force required to elicit paw withdrawal response in 50% of animals based on statistical formula
Note: Begin testing with filament estimated to be close to 50% withdrawal threshold. If no response, test next filament with higher force.
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”
Assess facial expressions for grimace scale
Evaluate spontaneous pain-like behaviors through assessment of facial expressions as non-stimulus evoked nociception measure
Note: Grimace scale is a non-stimulus evoked method used to assess spontaneous pain behaviors without external stimulus application
View evidence from paper
“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.”