It may be as quiet as, well, a mouse, but mice apparently can cough, new research finds. The findings suggest the rodents could be used in research to fight coughing in humans.
Rodents make ideal lab animals because they grow quickly, reproduce in large numbers and are small enough to house easily, allowing scientists to form experiments on them en masse. Mice are often used in research to develop new medicines for people — for instance, mice grimace when in pain, just like humans, and experiments that analyze their faces could help test out new painkillers.
It was a mystery as to whether mice can cough, since any such sounds would probably be barely audible at best. To help resolve this controversy, scientists at Guangzhou Medical College in China exposed 40 mice to fine mists of capsaicin, the molecule that makes chili peppers spicy. These mice were each placed in a machine known as a plethysmograph, a device that measures changes in body volume to detect when air moved in and out of the mice. The researchers also listened to mouse sounds with mini-microphones and watched the mice to monitor their body movements.
The rodents made a variety of sounds while sniffing, tapping their teeth, scratching their noses and twitching their heads. Among these sounds, the scientists identified explosive noises that coincided with the abrupt head-tossing, abdominal jerking and opened mouths one would expect with coughs.
When given cough suppressants such as codeine, mouse coughing dropped dramatically. Capsaicin given before the experiment also helped suppress coughing during the experiments, likely by desensitizing the mice's nerves.
These findings suggest mice could be used in experiments looking for cough syrups and other medicines to fight coughing. Currently, guinea pigs are used for such tests, but they can be relatively expensive compared with smaller mice.
Recently, scientists have found that mice can sing ultrasonic melodies and rats laugh when tickled. This research adds to behavior people might not think rodents are capable of, said behavioral neurobiologist Erich Jarvis at Duke University Medical Center, who did not take part in this coughing research.
"It would be interesting to see if it's possible to get mice to voluntarily cough, and if so, what are the neural mechanisms in the brain for that," Jarvis told LiveScience. "If they can voluntarily cough, maybe the neural circuits for such coughing could be the precursors for their vocal communication circuits."
The scientists detailed their findings online March 21 in the journal PLOS ONE.