Studies on the role of ACTH and of 5-HT in anxiety, using an animal model

The effects of ACTH (5 & 7.5 microgram/100 g) were studied using a new animal model of anxiety. ACTH had an anxiogenic effect that was maximal during a 10 min test period starting 3 min after injection. The behavioural effects of ACTH were counteracted by chronic administration of chlordiazepoxide (5 mg kg-1 for 5 days) and by acute administration of ethanol (0.4 g kl-1). These anxiolytic drugs decreased the turnover of 5-HT in the midbrain, hypothalamus and cerebral cortex, whereas ACTH increased 5-HT turnover in the midbrain and hypothalamus. Is it therefore proposed that anxiety results from the action of ACTH, possibly on 5-HT pathways in the midbrain and hypothalamus.