Influence of adrenocorticotrophic hormone on the behaviour in the swim test of rats treated chronically with desipramine.

Chronic desipramine (DMI) administration induced a dose-dependent reduction in the immobility time of the swim test in rats. A combined treatment of ACTH (50 iu kg-1 s.c.) and DMI (5 or 10 mg kg-1 i.p.) for 7 days potentiated the anti-immobility effect of DMI. ACTH 4-10, a fragment peptide with little corticotrophic activity, mimicked ACTH-induced potentiation. No stimulating effect on locomotor activity was observed following seven daily co-administrations of ACTH or ACTH 4-10 and DMI (10 mg kg-1). This behavioural evidence indicates that ACTH potentiation involves a central mechanism and demonstrates a functional interaction between ACTH and DMI at the behavioural level.