The Rat Grimace Scale: A partially automated method for quantifying pain in the laboratory rat via facial expressions

2011

The Rat Grimace Scale: A Method for Measuring Pain in Rats

Sample size: 10 publication 10 minutes Evidence: high

Author Information

Author(s): Sotocinal Susana G, Sorge Robert E, Zaloum Austin, Tuttle Alexander H, Martin Loren J, Wieskopf Jeffrey S, Mapplebeck Josiane C S, Wei Peng, Zhan Shu, Zhang Shuren, McDougall Jason J, King Oliver D, Mogil Jeffrey S

Primary Institution: McGill University

Hypothesis

Can the Mouse Grimace Scale be adapted for use in laboratory rats to quantify spontaneous pain?

Conclusion

The Rat Grimace Scale is a reliable and accurate method for quantifying spontaneous pain in laboratory rats.

Supporting Evidence

The Rat Grimace Scale demonstrated high inter-rater reliability with an ICC of 0.90.
The scale was able to detect dose-dependent analgesic effects of morphine.
Facial expressions were recorded using high-resolution digital video.
Rats showed significant increases in grimacing scores at various time points post-injection.
The automated software, Rodent Face Finder®, improved the efficiency of image extraction for scoring.
Baseline RGS scores were consistent across different pain assays.
All four action units of the RGS were equally effective in detecting pain.
RGS scores returned to baseline levels within a specified time frame after pain induction.

Takeaway

Scientists created a way to tell when rats are in pain by looking at their faces, just like how we can tell when someone is hurt by their expressions.