A Square Solution to Handling Mice

Mice are the most common animal used in research. Many routine procedures (including blood pressure measurement, injections, and blood collection) require the mouse to be restrained. As manual restraint can be stressful and traumatic, mice are most commonly held in a restrainer—typically a hard, smooth cylinder or cone. While the mice can be trained to enter these restrainers, they are inherently uncomfortable and the round sides do not provide any grip, leaving the mouse with a continuous loss of balance. Thus, many mice will refuse to enter a restrainer. At best, this discomfort can lead to aberrant results, as the mice constantly move. Often, mice will need to be additionally restrained, resulting in even more stress. At worst, mice have been known to panic in the restrainer, resulting in trauma, as they try to wriggle out.

These observations led Janet Wolforth, a veterinary technician at the University of Michigan, to look for better solutions. When she could not find an existing one, she invented the Laboratory Animal Cube (LACube). The LACube’s square interior, with a textured floor, was designed to be more comfortable and safer for the mice, while providing versatility for different procedures, potentially leading to better results for the scientists. In 2015, she received an AWI Refinement Grant to test the LACube.

Her proposal compared the LACube to the most commonly used cylinder to determine if it would improve restraint by 1) reducing stress of mice within the restrainer, indicated by ease of entry into the restrainer and less struggling while restrained; 2) improving ease of use by the animal handler; and 3) reducing variability of a noninvasive blood pressure measurement.

The results of this pilot study were encouraging. Within one day, most mice readily walked into the LACube (compared with an average of three days of training for the cylinder). Similarly, with the cylinder, acclimation takes at least three days before measurements can be done. With the LACube, the acclimation period was decreased to two days, since the mice more readily entered the device and were able to grip the textured surface, providing them with extra security. Once in the LACube, the mice remained calm during blood pressure measurement, moving much less and requiring no additional restraint. Blood pressure results were 15 percent lower for male mice and 4 percent lower for female mice in the LACube when compared with the cylinder.

The results suggest that the LACube is more comfortable to the mice (based on a greater willingness to enter the restrainer) and less stressful (based on the lower blood pressure readings). The results were promising enough that other researchers at the University of Michigan are inquiring about using the square restrainer. Ms. Wolforth will be submitting the results for presentation at national conferences and is planning to market the device.