Evaluating the Facial Expressions of Mice to Develop Better Pain-Relief Drugs

The research illustrates that mice express pain through facial expressions that are similar to humans. The scientists used the information to begin developing a Mouse Grimace Scale that could provide information for better treatments for humans and improve conditions for lab animals.

Dr. Jeffrey S. Mogil, who performed the study, said that using a Mouse Grimace Scale to accurately measure pain in mice is important in understanding spontaneous pain, which is one of the most prevalent symptoms of chronic pain.

"The Mouse Grimace Scale provides a measurement system that will both accelerate the development of new analgesics for humans, but also eliminate unnecessary suffering of laboratory mice in biomedical research," Mogil said, in a press release. "There are also serious implications for the improvement of veterinary care more generally."

The team analyzed images of mice before and during moderate pain stimuli. The level of pain was as strong as a common headache or the pain associated with a swollen finger. These images were then sent to a lab where facial pain coding experts analyzed them and created the scale. Five facial features were scored: orbital tightening (eye closing), nose and cheek bulges and ear and whisker positions according to the severity of the stimulus.

Experiments will continue on in the lab to investigate the efficacy of the scale and whether it will work well with other species, whether the analgesics given to mice after surgery work well at their prescribed doses, and whether mice respond to the facial pain cues of other mice.

A study that evaluated the facial expressions of mice during painful stimuli could lead to the development of new pain-relief drugs for humans, according to scientists at McGill University, who performed the study published in the journal Nature Methods.