| The forced swim test (FST) is a behavioral paradigm that has been developed to screen the potential anti-depressant properties |
| of compounds. |
| In the original version of the test, developed by Porsolt and his colleagues [2], a rodent is placed in a beaker (width: >20 cm; |
| depth ~15–18 cm) filled with water of 24 ± 2 degrees °C. The rodent is let to swim for 15 minutes. Escape from the beaker is not |
| possible. After the session, the animal is removed from the water, dried, and placed back in the home cage. Twenty-four hours |
| after the initial swim experience, the rodent again is placed in the beaker. During this second swim experience, that usually lasts |
| 5 minutes, most animals start showing passive behavior soon; they stop swimming and show little if any attempts to climb the wall |
| of the cylinder or to dive. When this occurs, the animal is said to be immobile or that it floats. The time from placement in the |
| cylinder to immobility/floating, often also expressed as the latency to immobility or the percentage of time that the animal |
| stays immobile, is regarded as the main outcome measure of the FST experiment. |
| Over the years, the original version of the FST has undergone some modifications. One major modification is that many studies |
| choose to use a beaker with a depth of 30 cm (instead of only ~15–18 cm). The prime reason for this is that the rodent is not able |
| to remain stable, without swimming, through tail contact with the bottom of the beaker. A second modification on the classical |
| FST is the use of the test to measure immobility/floating in a single session, thus without the 15 minutes pretest. It has been |
| suggested that the pretest is necessary in order to reliably and more quickly detect the immobile posture of the rodent during |
| the 5-minute test session 24 hours after the 15-minute test session. However, a single swim session may be sufficient to induce |
| stable immobile behavior, in particular for mice. Hence, some studies apply only a single swim session to discern immobility. |
| For more information on the protocols according to which the FST is used, we refer to Porsolt et al. [2, 3] and Slattery and |
| Cryan [5]. |
