Forced Swim Test

The forced swim test (FST), originally described by Porsolt et al. (1977), is the most widely used preclinical screen for antidepressant-like activity. An animal is placed in an inescapable cylinder of water and, after initial vigorous escape attempts, transitions to a characteristic immobile posture — floating passively with only minimal movements to keep the head above water. This immobility is interpreted as behavioral despair and engages circuits spanning the prefrontal cortex, dorsal raphe nucleus, locus coeruleus, and hypothalamic-pituitary-adrenal axis. The standard rat protocol uses a 15-minute pretest on day 1 to establish stable baseline behavior, followed by a 6-minute test on day 2, while the mouse version typically employs a single 6-minute session.

The primary dependent variable is total immobility time during the test session, typically scored during the final 4 minutes of the 6-minute test (the first 2 minutes are considered acclimation). Active behaviors are subdivided into swimming (horizontal movements across quadrants, predominantly serotonergic sensitivity) and climbing (upward-directed movements against the cylinder wall, predominantly noradrenergic sensitivity). The ratio of swimming to climbing time provides pharmacological specificity beyond what immobility alone reveals. Latency to first immobility episode is a secondary measure of despair onset kinetics.

ConductMaze automates the FST using overhead and side-view camera tracking to distinguish immobility, swimming, and climbing in real time without manual scoring. The software applies validated posture-recognition algorithms calibrated to species-specific movement thresholds, bins data into user-defined time epochs, and exports cumulative behavior timelines. Automated water temperature monitoring and cylinder fill-level verification ensure standardized conditions across cohorts.