Models of Depression

Porsolt Forced Swim Test.   The forced swim test or behavioral despair test is the most commonly used test to measure the effects of antidepressant treatment.  The characteristic behavior of the test, termed immobility, develops when a rodent is placed in a tank of water for an extended period of time and “makes only those movements necessary to keep its head above water” (Porsolt et al., 1977).  The development of immobility is usually facilitated by a pretest for 15 min given 24 h before a 5-min test.  When antidepressants are administered between the pretest and the test, antidepressant drugs decrease immobility.

Forced swim sessions are conducted by placing rats individually in large glass cylinders (45 x 20 cm) containing 24-25 C water approximately 30 cm deep.  The water should be at a height such that the rat cannot escape or touch the bottom of the beaker.  On day one, the rat is placed in the cylinder for 15 min followed by a second 5 min test 24 hr later.  Latency to float and amount of time spent struggling are measured.  The 5 min test on day two is video recorded and later scored by a blind observer. 

During the entire duration of the task the experimenter is present and watching the rats.  If there is any indication that the animal is in danger of drowning, it is immediately removed from the beaker and excluded from the study.  At the end of the swim session the rats are towel dried and placed in a clean cage.  The water in the test arena should be changed between each subject.

The RNL has 4 Porsolt Arenas manufactured by Stoelting.  The chambers measures 45 cm in height and 20 cm in diameter.  The arena accommodates both top and side camera placement.