Animal behavioural studies in the evaluation of antidepressant drugs

Animal behavioural models of psychiatric disorders cannot exactly simulate human psychopathology, but they can be used to evaluate the behavioural changes induced by drugs and to suggest hypotheses about the functions of the CNS and its involvement in psychiatric disorders. This should lead to a more heuristic classification of psychotropic drugs and to clarification of their therapeutic possibilities. The following animal models simulate aspects of depressive disorders and are sensitive to the antidepressant effects of drugs. (i) The forced swimming test: described as 'behavioural despair' on the assumption that the animal has given up hope of escaping. (ii) The 'restraint stress' test: this may indicate a failure to adapt to stress. (iii) The learned-helplessness model: exposed to uncontrollable events, animals exhibit learning performance deficit and behavioural changes, including decreased locomotor activity and loss of appetite. (iv) Waiting behaviour: improvement in the ability to wait for and/or postpone an active response; this could be related to the reported beneficial effects of antidepressants on impulsive behaviour.