Tail or tunnel? Mouse-handling methods could influence experiments
As you might remember from high school chemistry class, it's important to take every component into account when designing scientific experiments. But it turns out that researchers may have been overlooking something when working with mice: the way in which the rodents are handled prior to the start of an experiment. A new study shows an advantage to a particular method of getting mice into a testing arena that could remove a stumbling block to accurate research.
It turns out that mice don't really like being picked up by their tails. That's the conclusion previously reached by University of Liverpool researchers Kelly Gouveia and Jane Hurst, who determined that the practice induces anxiety. Instead, the researchers found, coaxing mice into a clear tube and then transporting them inside that tube seems to reduce the rodents' stress levels.
In the most recent research, the duo was interested in finding out whether the way in which mice are handled would have an impact on experiments. So they designed an experiment of their own.
In it, female mouse urine was spread in regions of a testing field and then male mice were set loose to explore. Some of the mice were brought to the test by their tails, while others were either carried in cupped hands or transported in the clear tube.
In the cases of the tail-toted mice, exploration was extremely low. In fact, so many of the mice carried this way failed to sniff the urine or explore at all, that it was a challenge for researchers to assemble enough data to reach statistical significance for their study.
The mice that were brought to the experiment inside the tube, however, were extremely active and investigated the urine-soaked areas vigorously.
What's more, the experiment was carried out three times on both sets of mice. In the case of the more active tube-handled mice, by the third time, their interest in the scent diminished because of familiarity. However, when the scent was swapped out for different urine on a fourth try, the mice explored with renewed gusto. The tail-carried mice didn't show much interest in any of the tests and did not become more active when the new scent was introduced in the fourth pass.
The mice that were scooped into the hand exhibited too broad a range of reactions for the researchers to draw a conclusion about its efficacy as a transportation method.
The researchers say that discovering the ways in which a simple change in handling methods influenced the behaviors of the rodents could be key in eliminating an important element of variability in scientific research that relies on mice.
"The method used to pick up laboratory mice has a surprisingly strong influence on their anxiety, and our study shows that this has a major impact on the reliability of their behavioral response to test stimuli," said Hurst. "A simple change to picking up mice up in a tunnel rather than by the tail could have a really positive impact on the wide range of research that relies on behavioral testing, as well as improving the wellbeing of test animals."
Hurst has developed a mouse-handing tutorial for researchers that has been posed on the National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs) website. The organization, which advocates for the wellbeing of lab animals, funded the work and has also declared 2017 the "Year of Laboratory Rodent Welfare."
The new work has been published in the journal Scientific Reports.