Mice and Rats “R” Us: The Back Story of Horrible Rodents

Did you wonder why the researchers use mice and rats in experiments when the results are often applied to humans, ischemic and hemorrhagic strokes and TBIs among them?

I wondered why, and I thought the reason was because the researchers would proceed with “all mammals are alike to some degree,” and the vermin are cheap and few people care enough about them (except the People for the Ethical Treatment of Animals–PETA). So I went ahead and did what I do best: Research. 

It turns out that mice, rats, and humans are eerily alike. Rattus norvegicus turns out to have 2.75 billion pairs of DNA bases (chemical bonds). That is slightly fewer than human 2.9 billion and slightly more than the mouse’s 2.6 billion.

Similarities between the human and rat genomes (entire set of DNA instructions found in a cell) are  important. Researchers were satisfied to find that almost all the human genes linked with disease so far are identical in rats, too, upholding the use of rats in their testings. All three species–humans, mice, and rats–share 280 large chunks of chromosomes that are virtually identical, indicating that they are requisite for comparison. 

When a female mouse gets pregnant, it only takes between 19 and 21 days for her to give birth to a litter which is an average 6 to 8. When a female rat gets pregnant, the average gestation time is 21 to 23 days, and the usual litter size is 8 to 18 pups. So it makes sense to use them.

Among the thousands upon thousands of experiments, for example, mice have been used to show that drug abuse leads to permanent changes in the brain. Rat experiments led to cardiovascular advances, neural regeneration, wound healing, diabetes, and an assortment of behavioral studies. And both mice and rat are the two most commonly used mammalian models for studying strokes and TBIs. 

So the next time you trap mice or rats and lead them to their deaths, know that in the laboratories, there are plenty more vermin promoting wellness for humans. The PETA people are angry, but others are delighted to have one less pest in the home. In a perfect world, vermin belong in the laboratories. Period.