The tail suspension test is a procedure that has been developed as a model for depressive-like behavior in rodents. In this particular setup, a mouse is suspended by its tail for 6 minutes, and in response the mouse will struggle to escape from this position. After a certain period of time the struggling of the mouse decreases and this is interpreted as a type of learned helplessness paradigm. Animals with invalid data (i.e., climbed their tail during the testing period) are excluded from analysis.
The tail-suspension assay is a mainstay for the discovery and validation of novel antidepressants. Knockout of the noradrenalin transporter, one target of the antidepressant bupropion, demonstrates an increased struggle time in the tail suspension assay (Xu et al., 2000). The tail suspension assay has been automated; giving it added objectivity and making it appropriate for high throughput analysis. The tail suspension assay measures the efforts of the subject to extricate itself from an inescapable situation, i.e. it measures a tendency toward ‘giving up’. Compounds known to reduce depressive symptoms in patients reduce the immobility time in tail suspension, therefore gene knockouts that result in decreased time spent being immobile, in the absence of any general increase in activity levels (as measured in assays such as the open field), point to excellent opportunities for the discovery of novel therapeutics for the treatment of depression. In this particular setup (PHM-300 Tail Suspension Test Cubicle) a mouse is suspended by its tail for 6 minutes, and in response the mouse will struggle to escape from this position. Extended struggle is taken as anti-depressive behavior, whereas curtailed struggle is interpreted as depressive.
Displayed below is a sample graph of how tail suspension observations are presented. In comprehensive phenotypic data packages graphs are interactive. Raw or calculated data and statistics can be seen by clicking on points in the graph.
Figure illustrates median immobility (seconds) of male and female (left), male (center), and female (right) mutant mice. Median response times for wild type littermates (green circle), homozygous (red diamond), and recent historical wild types (purple line) are plotted against long-term historical median immobility times (+/- 2 standard deviations) for wild type animals (green shading). Recent wild type values are calculated from data collected within 60 days of current measures and long-term historical values are derived from data collected on more than 10,000 wild type mice.
Xu F, Gainetdinov RR, Wetsel WC, Jones SR, Bohn LM, Miller GW, Wang YM, et al. (2000) Mice lacking the norepinephrine transporter are supersensitive to psychostimulants
, Nat Neurosci, 3:465-471