Enhanced behavioural, electrocortical and hyperthermic effects of serotonin-like agents after impairment of serotonin transmission in fowl brain.

In adult fowls and in young chicks (Gallus domesticus) the effects were studied on body temperature, behaviour and electrocortical activity of 5-HT and other direct or indirect serotonin agonists given into the III cerebral ventricle in conditions of prolonged impairment of serotoninergic transmission. In chicks pretreated with 5,6-dihydroxytryptamine the subsequent intraventricular injection of 5-HT produced more intense and longer-lasting hyperthermic response and behavioural and electrocortical sleep. On the other hand fenfluramine given intraventricularly in fowls pretreated with 5,6-DHT did not produce significant body temperature and behavioural changes. After 14 and 21 day treatment with methysergide the subsequent administration of 5-HT, fenfluramine and quipazine produced in fowls an hyperthermic response and behavioural sleep more marked and longer-lasting than in control animals. The present experiments show that in conditions of chronic impairment of 5-HT function there is an enhanced behavioural and body temperature response to 5-HT and drugs acting by releasing endogenous 5-HT or 5-HT agonists.