An automated analysis of rat behavior in the forced swim test

The Porsolt forced swim test (FST) is a commonly used paradigm to evaluate antidepressant activity of drugs. This test is based on visual measurement of the rat's floating time (FT) in a tank filled with water. Here, we present an automated, accurate and faster method for estimating FT by the distance moved (DM) by the animal via the use of the Ethovision software in three separate experiments. Experiment 1 investigated the effect of varying delays (24-h and 7-day) between pretest and test on FT and DM. Experiment 2 aimed at examining the effects of a 2-day withdrawal period in rats sensitized to amphetamine and cocaine, on FT and DM. Finally, Experiment 3 looked at the effects of desipramine and fluoxetine on FT and DM. The results of these experiments show that increasing the delay between pretest and test reduced FT during subsequent exposure (test). In addition, rats sensitized to and then withdrawn from either amphetamine or cocaine did not differ in FT or DM compared with control rats. Finally, both desipramine and fluoxetine reduced FT and increased DM. Furthermore, DM was consistently significantly negatively correlated with FT. These results support the use of an automated method for the evaluation of rat behavior in FST.