Renowned international and German animal rights organizations have been fighting for years for a ban on the forced swim test. It was developed in 1977 by Roger Porsolt and colleagues as a model for predicting the clinical efficacy of antidepressants. Today, it is used in basic research, in the pharmaceutical screening of potential antidepressant drugs and to assess depression-like behavior in animal "models". The test is based on the assumption that an animal placed in a container filled with water initially tries to escape but eventually shows immobility, which is seen as a measure of distressed behavior.

Rat in a forced swim test.
Credit: Wikipedia.

Such tests are still permitted in Germany: Here alone, 21 applications involving almost 15,500 rats and mice were approved between 2017 and 2023. Numerous people have spoken out in favor of a ban in European signature campaigns.

The swimming tests are used again and again for reasons of tradition - apparently because everyone in the research field does it this way. And that is one of the problems: "According to recent studies, swimming tests are very stressful and do not have the informative value that is often attributed to them," says Dr. Christiane Hohensee, head of the InVitro+Jobs science platform.

Despite its attractiveness due to its simplicity, this model has a number of disadvantages. In drug assessment, the reinforcing effect of chronic administration cannot be demonstrated in this test. In addition, the aversion that test animals develop to the test leads to biased test results. The Forced Swim Test is also considered by the pharmaceutical industry to be inaccurate for identifying new antidepressants. Studies have shown that of 109 active substances identified in the animal test, only 28% had been tested for their antidepressant effect in humans. Scientists have expressed considerable concerns in studies regarding its theoretical and predictive validity. For example, the forced swim test mainly assesses coping strategies in an unavoidable situation.

In most cases, the experiments were incorrectly described and approved in animal testing applications as being only moderately stressful. And the result is disproportionate to the high stress to which the animals are exposed, because they do not know whether they will ever get out of the water basin without an exit. According to Article 15 (2) of the European Animal Experiments Directive 63/2010/EU, Member States must ensure that a procedure is not carried out if it causes severe pain, suffering or distress which is likely to be prolonged and cannot be alleviated.

Quellen:
(1) https://www.parliament.nsw.gov.au/bills/Pages/bill-details.aspx?pk=18431
(2) https://www.nhmrc.gov.au/research-policy/ethics/statement-forced-swim-test-rodent-models
(3) https://cosmosmagazine.com/people/ethics/top-medical-research-body-says-these-two-tests-on-mice-and-rats-should-end/
(4) https://www.animaltestinfo.de/
(5) https://www.schwimmen-bis-zur-verzweiflung.de/
(6) Yankelevitch-Yahav R, Franko M, Huly A, Doron R. The forced swim test as a model of depressive-like behavior. J Vis Exp. 2015 Mar 2;(97):52587. doi: 10.3791/52587. PMID: 25867960; PMCID: PMC4401172.
(7) Trunnell ER, Carvalho C. The forced swim test has poor accuracy for identifying novel antidepressants. Drug Discov Today. 2021 Dec;26(12):2898-2904. doi: 10.1016/j.drudis.2021.08.003. Epub 2021 Aug 12. PMID: 34390862.
28287253; PMCID: PMC5518600.
(8) Commons KG, Cholanians AB, Babb JA, Ehlinger DG. Der Rodent Forced Swim Test misst die Stressbewältigungsstrategie, nicht das depressionsähnliche Verhalten. ACS Chem Neurosci. 2017 May 17;8(5):955-960. doi: 10.1021/acschemneuro.7b00042. Epub 2017 Mar 22. PMID: 28287253; PMCID: PMC5518600.