Description
When rodents are forced to swim in a closed space from which they cannot escape, they will eventually stop attempting to escape and become immobile (except from small movements to keep their heads above the water). The immobility is thought to reflect a state of despair. In this task the rodents (typically rats) are individually placed in a vertical cylinder containing water, maintained at 25簞C for a set length of time (usually 15 minutes). Twenty-four hours later, the subjects are placed in the same cylinder and during a five-minute testing period, the time spent immobile is measured. The subject is considered immobile whenever it remains floating passively in the water in a slightly hunched but upright position, with its head just above the water surface.
Purpose
The test is quite sensitive to antidepressant drugs and is now used routinely as a
method for screening novel compounds. An effective antidepressant agent will stimulate
the animal to swim and attempt to escape for much
longer periods of time (i.e., compared to placebo controls).