Is antidepressant efficacy revealed by drug-induced changes in rat behaviour exhibited during social interaction?

Remission from depressive illness is associated with a modification in patients' behavioural reactions to environmental/social stimulation, and requires continuous drug treatment. We have examined the effects of antidepressant drug treatment and repeated electroconvulsive shock (ECS) on the behaviour of rats during social interaction (SI) to determine whether antidepressant treatments modify behavioural patterns of experimental animals that may be related to their ability to modify reactive human behaviour. Acute treatment of short-term isolated resident rats with nonsedative doses of antidepressant drugs, or sedative doses of haloperidol and diazepam, dose relatedly reduced aggressive behaviour exhibited during SI. Conversely, chronic antidepressant treatment (including ECS), but not chronic haloperidol or diazepam treatment, increased the aggressive behaviour of resident rats. These studies have revealed selective, diametrically opposite, effects of acute and chronic antidepressant treatment on rodent aggressive behaviour that may be indicative of antidepressant efficacy. The effects of chronic antidepressant treatment in particular may indicate a disinhibition of rodent social behaviour which may mirror the externalisation of emotions associated with the remission of depressive illness.