Forced swim test case study

The forced swim test or forced swimming are experimental procedures in which rats or mice are placed into a container of water with no means of escape. The rodents will first try to escape before settling down, and floating or swimming steadily. The test is used by researchers at the University of Bristol to understand the neurobiology of stress.

About the forced swim test

The swimming is classed as a forced procedure because it is not a voluntary behaviour of the animal. Swim times are kept to the minimum required to achieve the scientific aims of the research (a maximum of five minutes for mice and six minutes for rats). Animals may stop swimming and float during the short test, but this is an adaptive response to not being able to escape and not due to exhaustion.

The animal is observed during the full duration of the test. At the end of the study, the animals are humanely killed using a legally approved method so that tissues and/or blood can be collected for scientific analysis essential to the research.

Response to criticism of the test

We recognise there are differing views about the use of animals in research, including some concerns around whether it is ethical.

The forced swim test and forced swimming have been approved as valid models to study the neurobiological processes underpinning how the brain deals with and adapts to stressful challenges. Increasing our understanding of these processes is important because stress is known to contribute to the development of major depression and many other stress-related illnesses. A better understanding of how we respond and adapt to stressful events in our lives is crucial for the development of new treatments for stress-related disorders.

A recent report from the Animals in Science Committee (ASC) - an advisory non-departmental public body that provides independent advice to the Home Office - found that the use of the forced swim test was justified when studying the neurobiology of stress because it 'may in the longer-term lead to benefits for humans, animals or the environment'.

The report also highlighted that there are 18 project licences in the UK that authorise the use of the test. There was no evidence of mice or rats drowning during or after the test in the UK and no animals were swum to exhaustion.

The ASC report also supports the use of the forced swim test for the screening of potential antidepressants but advises it is not justified as a model of depression or to study anxiety. Bristol does not use forced swimming in any of these contexts.

Wherever possible we rely on non-animal methods, for example computer models, cells grown in the laboratory or human volunteers. When these methods are not suitable to address the scientific gaps in knowledge, we use animals in research to improve our understanding of health and disease in both humans and animals. At present, there are no non-animal alternatives to the forced swim test.

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