Use of the automated tail suspension test for the primary screening of psychotropic agents.

Mice, when suspended by the tail, will alternate between active attempts to escape and immobility. A specially developed computerized device (ITEMATIC-TST) automatically measures the duration of immobility of 6 mice at one time and at the same time provides a measure of the energy expended by each animal, the power of the movements. Use of these 2 parameters enables activity profiles to be generated which can distinguish different classes of psychotropic activity. Immobility is decreased by antidepressants and psychostimulants, but increased by neuroleptics and minor tranquillizers. Minor tranquillizers can be distinguished from neuroleptics in that they decrease the power of the movements, whereas neuroleptics are without effect on this parameter. The present experiments were undertaken to see whether the activity profiles generated in this procedure could indeed be useful for primary psychotropic screening. Eighteen compounds, including antidepressants, neuroleptics, minor tranquillizers, sedative/hypnotics, dopaminergic stimulants and 3 dummy compounds were first submitted to a shortened primary observation procedure for dose finding and were then investigated at 2 doses in the automated tail suspension test. All experiments were conducted blind. The results obtained largely confirm the activity profiles already reported in this test and show that the combined use of primary observation and the automated tail suspension test permit the unambiguous identification of the pharmacological activity of 15 of the compounds tested with tentative identification of the 3 remaining compounds.