Tryptamines and some other substances affecting waking and sleep in fowls.

1 Adult fowls (Gallus domesticus) with cannulae chronically implanted in the IIIrd cerebral ventricle and various other sites of the brain, received infusions or injections of tryptamines and catecholamines into the brain; effects of and interactions between these substances on behaviour, electrocortical activity and body temperature were studied. Reserpine-induced arousal, was investigated in young and adult fowls. 2 Tryptamine and alpha-methyltryptamine, given intraventricularly or into the hypothalamus of intact fowls evoked behavioural and bilateral electrocortical arousal, postural changes, elevation of body temperature and tachypnoea; behavioural and bilateral electrocortical arousal were obtained with infusions into the mesencephalon. Ipsilateral electrocortical arousal only, resulted from infusion of alpha-methyltryptamine into the hypothalamus or mesencephalon of fowl encephale isole preparations. The above effects in intact fowls were reduced or replaced by sleep following administration of noradrenaline or alpha-methylnoradrenaline into the IIIrd ventricle or hypothalamus. Pretreatment of intact fowls with an amine oxidase inhibitor surprisingly attenuated or reversed the excitant effects of intraventricular tryptamine. 3 5-Hydroxytryptamine (hydrogen maleinate, creatinine sulphate or oxalate) given intraventricularly or infused into the hypothalamus, elevated body temperature; tachypnoea and postural changes developed at some stage during the elevation of body temperature. Sleep also was induced, although with the oxalate this was succeeded by marked arousal. 4 Behavioural and electrocortical sleep induced by 5-hydroxytryptamine infused into the hypothalamus were replaced by arousal on infusing tryptamine into the hypothalamus, and vice versa. 5 Dexamphetamine infused into the hypothalamus induced drowsiness or sleep which even reversed arousal elicited by systemically administered dexamphetamine. 6 Reserpine-induced arousal was achieved in young and adult fowls pretreated with mebanazine; this arousal was attenuated or replaced by sleep following intraventricular noradrenaline or dopamine but not by 5-hydroxytryptamine nor by noradrenaline or dopamine applied to the hypothalamus. Prenylamine also induced arousal following pretreatment of chicks with mebanazine.