(Updated November 11, 2019.) Pfizer, the world’s third-largest pharmaceutical company, will no longer conduct forced swim tests on animals.
International animal rights organization PETA (People for the Ethical Treatment of Animals) notes that the pharma giant used at least 1,270 mice and rats in forced swim test experiments since 1991.
What Is the Forced Swim Test?
Pharmaceutical companies use the forced swim test, also known as the behavioral despair test, to test the efficacy of antidepressant drugs. Experimenter Roger Porsolt popularized the test in 1977 and concluded that animals in “despair” swam for less time.
In order to carry out the test, mice or rats are placed in an inescapable tank filled with water so that researchers may measure their “escape related mobility behavior,” according to the Journal of Visualized Experiments. They are injected with antidepressants before the test.
Is the Forced Swim Test Ethical?
The journal maintains that the protocol for the experiment ensures minimal impact on the animal’s stress levels. According to the first point of protocol, the cylindrical tanks should be filled in a way that mice are unable to swim to the bottom and high enough so that they cannot escape. PETA notes that animals used in the experiment frantically try to escape by climbing up the side of the cylinder or by diving underwater in search of a route.
Scientists record only the last four minutes of the six-minute test. Protocol claims that this is because most mice are active at the start and the “potential effects of the treatment can be obscured during the first two minutes.”
After struggling for some time, most give up and allow themselves to float in the water. This is called “behavioral despair,” or a situation in which the animal loses all hope to escape a stressful situation.
All the while, the struggle is recorded. Many tanks are also divided, so that several mice can be used at a time. A white noise generator is used to avoid “startling” the animals. After the test, protocol mandates drying the animals with a paper towel to prevent hypothermia.
Does the Forced Swim Test Work?
Questions surrounding the effectiveness of the test stretch back decades and there are multiple scientific papers investigating whether it is a suitable method for obtaining results. The forced swim test may not be effective for a number of reasons.
One 1988 study from the journal Psychopharmacology, titled, “Is the forced swimming test a suitable model for revealing antidepressant activity?” drew upon prior research that shows there’s no relationship between the inescapability of the tanks used “immobility” — the term used to describe how mice and rats may give up during the test.
According to protocol, mice will “readily” float in the water and may sometimes only make small motions to keep their heads above the surface. While some scientists interpret the lack of struggle as a sign of depression, others say that it shows the animals have adapted to a new environment. Rats are known for being less fearful in subsequent forced swim tests. “It seems that the forced swimming test does not satisfy ‘psychic’ symptoms [of depression], since the rat does not appear to be desperate or to feel helpless,” the study notes.
Same Dosage, Different Results
The study also describes the measure of immobility is entirely subjective — or, up to the person viewing the recording. Floating in water — which mice can readily do — is not to be considered a sign of mobility. Sometimes after a single bout of struggling to stay afloat, mice can drift in water as a result of momentum. If rats adapt to the stress, it’s considered a sign of “despair.”
Movements made by the observer can also potentially affect the outcome of the test if the mouse can see them.
The same dosage may yield different results. “For example: a) 30 mg/kg imipramine, injected only once 1 h before the test, may be either ineffective or effective and b) 10 mg/kg amitriptyline administered for 7 consecutive days may be either markedly or barely effective.”
None of the antidepressants used in swim tests have been approved for human consumption, yet. Neither rats nor mice are protected under the Animal Welfare Act — the U.S. is the only country to exclude them from laws protecting lab and research animals.
About Mice and Rats
Mice and rats are social, adaptable creatures by nature that will build relationships with their cage-mates in a variety of ways. They sleep in groups for bonding, warmth, and security. Just like us, mice and rats have a wide range of emotions and enjoy playing with their family members.
Both mice and rats are smart, curious animals that are affectionate toward their animal and human friends. They’re even capable of learning tricks for treats and can also learn their names and will come when called. Rats may also grieve the loss of their friends.
Rats exhibit empathy toward their fellow animals, according to multiple studies. In a 2011 experiment involving a rat trapped in a plastic tube, the animal’s unrestrained companion work to free the other rat. Some explained the behavior saying that it’s because rats crave friendship, but a 2015 study revealed that they may have an altruistic nature.
Researchers at the Kwansei Gakuin University in Japan developed a box divided by a transparent partition. On one side, a rat was forced to swim in the water. Although they were not at risk of drowning, they exhibited distress. The only way to escape was if the rat on the other side opened a small round door. The other rat opened the door in most cases. Next, experimenters added a tasty treat into the mix. This time, the rat on the dry side had the choice of two doors. One would free the other animal while the other led to chocolate. Rats chose to help their friends up to 80 percent of the time.
Rats Aren’t Dirty
Rats who have bonded with their human love to ride on shoulders or be pet, held, and even tickled. When tickled, they emit squeaks that scientists have pinpointed as a sign of joy. “Over time, the rats learn it is fun to play with this [your] hand, and they start chasing it and even recognizing it as a playmate, he says,” says Science Mag. Like dogs, lambs, cows, and rabbits, rats will exhibit “joy jumps,” where they’re so happy, they jump for joy.
Rats love to keep clean and groom themselves daily, as opposed to the stereotype that they’re dirty. They’re also less likely than cats or dogs to transmit parasites and viruses.
Don’t buy from a pet store if you’re thinking of bringing a mouse or rat into your life. Look into local rescue groups and read up on how to give your potential new companion a happy, healthy, and safe life.
Other Companies That Have Banned the Swim Test
Pfizer joins a growing number of companies that have banned the test.
The organization calls for major pharmaceutical companies such as Bristol-Myers Squibb, and Eli Lilly to end the practice. These companies have used at least 5,461 mice, 1,066 rats, 748 gerbils, and 305 guinea pigs in their experiments.
Roche — one of the world’s top ten pharmaceutical companies, committed to stopping the widely discredited forced swim test last June. Between 2001 and 2018, Roche published 11 papers indicating that it used the swim test on 800 mice and rats.
Pharmaceutical giant Johnson & Johnson stopped forced swim tests last March after working with PETA. It and one of its subsidiaries, Janssen, a Belgian pharma company, had conducted studies in recent years.
Dutch company DSM Nutritional Products, which manufactures ingredients for supplement and personal care products, ended the tests last May. It tested on more than 200 mice and rats to make claims about ingredients like oregano extract.
AbbVie, an American biopharmaceutical company, said it would no longer conduct or fund the tests last December.