When rats or mice are forced to swim in a deep cylinder with tepid water, they become nearly immobile and cease trying to escape.
Immobility is thought to reflect a state of “behavioral despair” and is reduced when rats and mice are treated with a wide variety of antidepressants.
Rodent models of depression are mainly based on predictive validity, objectivity of measured response and their high reliability and reproducibility.
Effects of SSRI and Tricyclic Antidepressants

The forced swim test in rats can differentiate between SSRI and Tricyclic-like antidepressants by their differential effects on climbing and swimming behaviors following sub-chronic intraperitoneal injection.
Effects of Double and Triple Reuptake Inhibitors
The triple uptake inhibitor DOV21947 and the double (serotonin / norepinephrine) reuptake inhibitor, venlafaxine, decrease immobility in the rat FS test following sub-chronic intraperitoneal injection.
Sertraline Decreases Time Immobile in BALB/cJ Mice
Sertraline, a Selective Serotonin Reuptake Inhibitor, decreases immobility of BALB/cJ mice in the FS test following acute intraperitoneal injection.