[Behavioral assessment of antidepressants (1)--The forced swimming test: a review of its theory and practical application].

Forced swimming test is now widely used as a screening method for antidepressant drugs since it was proposed by Porsolt in 1977. In this article, we at first reviewed its theoretical background and then pointed out various factors which could possibly affect the results. These include the apparatus used for the test (quality and size of cylinder), experimental animals (breeding condition, body weight, age and strain), method of drug administration and evaluation of animal's behavior (criteria for counting the immobility time and those for excluding variety of orienting or escape behaviors, such as jumping, climbing, diving, circling and extended sniffing behaviors). Finally, potential pitfalls and difficulty of the test were discussed based on our own experiences. We concluded that the various factors discussed in this article should be carefully controlled for the pertinent application of the forced swimming test.