Free the Mice!

“Can We Trust Research Done with Lab Mice?” by Barry Yeoman, in Discover Magazine (July 2003), Buena Vista Magazines, 114 Fifth Avenue, 15th Fl., New York, N.Y. 10011.

Rodents—those ancient instigators of shrieks, disgust, and bubonic plague—have always found acceptance in at least one human setting: the laboratory. Mice have long been the primary subjects of medical, drug, and learning studies, but some young scientists are challenging the scientific validity of lab experiments done with mice.

Led by the Swiss animal behaviorist Hanno Würbel, reports journalist Yeoman, these scientists aim to prove that the bare-bones environment of most lab mice—shoebox-sized cages with no amenities beyond food and water—have serious bio­­log­ical effects on the animals that may compromise findings that are applied to human conditions.

To gauge the consequences of this environment, Würbel set up 24-hour video cameras mon­itoring the behavior of lab mice. The after-hours conduct he found was comparable to that of a schizophrenic or autistic human: highly regimented, repetitive activities for no practical purpose. Mice did backflips for 30 minutes at a time, gnawed at cage bars ceaselessly, and ran in continual circles. Scientists call such movements “sterotypies.” Würbel thinks that actual changes in the physiology of the animals are manifested in these behaviors.

Stolen looks at the mice’s secret nightlife aren’t the only indicator that impoverished lab conditions may have a profound effect. One study found that lead-contaminated drinking water damages the brains of mice in barren environments, but not those in enriched ones. Another found that small amounts of light in the lab at night significantly accelerate tumor growth.

Genetic research is also affected. In 1999, a Prince­ton University team removed a gene associated with the N-methyl-D-aspartate receptor in the hippocampus, a component of the brain that is a critical tool in transforming short-term memories into long-term ones. But when they placed some of these memory-deficient mice in cages enriched “with running wheels, playhouses, and an ever-changing assortment of toys” for two months, the animals were magically able to remember again. As early as the 1950s, Mark Rosenzweig of the University of California, Berkeley showed that lab rats supplied with mazes, ladders, and sponges had increased enzyme levels, synaptic bridges, and cerebral weight.

Würbel stresses that he’s more interested in the good of science than rodent liberation. He says that science would be the better for developing a more complete concept of the animals used in testing, including their evolutionary background and natural function. “I have a vision that there will be a time when we will have natural-like, although heavily managed, populations of rats or mice, maybe in big enclosures, representing whole populations.”

Others reel at this suggestion. John Crabbe, a behavioral neuroscientist from Oregon, suggests that providing mice food, water, and clean bedding is plenty. Given that generations of mice have been raised in barren cages, perhaps that should now be considered their natural environment.