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Porsolt Forced Swim Test

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Purpose: The Porsolt swim test (PST) was developed as a rodent screening test for potential (human) antidepressant drugs. It is based on the assumption that an animal will try to escape an aversive (stressful) stimulus. If escape is impossible, the animal eventually stops trying and gives up. In the PST, the animal is placed in a cylindrical container of water from which it cannot escape. Most animals will attempt to escape by actively swimming. When the animal stops swimming and floats on the surface of the water it is considered to have “given up”. An animal that gives up relatively quickly is thought to be displaying characteristics similar to human depression. The validity of this test stems from the finding that physical or psychological stress (which can induce depression in humans) administered prior to the test causes animals to give up sooner and treatment with an antidepressant drug will increase the time an animal spends in escape attempts.

This link displays videos of animals in the swim task.

Species used: Rats and mice. Impaired swimming ability due to musculoskeletal or other abnormalities will affect performance in this test.

Important considerations

  1. Water depth and temperature
    1. The water must be deep enough so the animal cannot touch the bottom with its tail or feet. A depth of 30 cm is commonly recommended, although less depth may be adequate for mice.
    2. Water temperature should be 24-30⁰C2.
    3. Animals should be allowed to dry in a warm environment after removal from the water. Absorbent towel(s) may be placed in the holding cage to collect water dripping off the animal and a heating source directed over or underneath the cage may provide warmth. Do not attempt to towel- or blow-dry animals as this is stressful and rough handling can cause injury.
  2. Water changes
    1. Urine and fecal material will accumulate in the water and contribute to bacterial contamination and growth. The container should be emptied and disinfected after each day’s tests.
    2. Fecal material may be removed after each animal with a small mesh net.
  3. Test procedures
    1. A wide range of test session durations have been reported (4-20 minutes)1.
    2. Animals must be observed continuously during the swim test. Any animal that sinks below the surface should be removed from the water immediately2.

USDA category: E

Alternative tests: Tail-suspension test and others1,2,3.

References:

  1. Crawley JN. What’s Wrong With My Mouse? Behavioral Phenotyping of Transgenic and Knockout Mice, 2nd ed. Hoboken (NJ): Wiley; 2007.
  2. Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. Washington, DC: The National Academies Press; 2003. Available from: http://www.ncbi.nlm.nih.gov/books/NBK43327/
  3. Castagne V, Moser P, Porsolt RD. Behavioral Assessment of Antidepressant Activity in Rodents. In: Buccafusco JJ, editor. Methods of Behavior Analysis in Neuroscience. 2nd edition. Boca Raton (FL): CRC Press, 2009. Chapter 6. Available from: http://www.ncbi.nlm.nih.gov/books/NBK5222/