Mice were isolated for 7-9 days. An isolated mouse and a mouse reared in group show a difference in their behaviour when observed together under an inverted beaker. The isolated mouse makes one half escape attempts in regard to the grouped mouse. This is considered as a social behavioural deficit. 2. The effect of four tricyclic antidepressant drugs was tested on this social behavioural deficit. None of the following drugs acutely given: imipramine, desipramine, amitriptyline impaired the social behavioural deficit. Clomipramine reduced the deficit at the only dose of 2 mg/kg. The four antidepressants tended to increase the deficit at the high dose of 32 mg/kg but this may reflect a sedative effect. Chronic amitriptyline did not impair the social behavioural deficit. 3. It is concluded that acute and probably also chronic antidepressant treatments are without effect on the isolation induced social behavioural deficit test.
