Brain monoamines and adrenocortical activation.

1. The effect of a pharmacologically induced increase or depletion of brain monoamines (5-hydroxytryptamine, noradrenaline, dopamine) was investigated with respect to adrenocortical function.2. No strict correlation was found between the depletion of brain amine stores induced by prenylamine or p-chlorophenylalanine and adrenocortical activation, even at times in which the peak effect of brain amine depletion occurs.3. Restraint stress causes a manifest increase in brain 5-hydroxytryptamine while decreasing the cerebral noradrenaline and dopamine content. This stress strongly stimulates corticosterone secretion by the adrenals.4. A monoamine oxidase inhibitor, nialamide, at a dose which causes an evident increase in brain amine concentrations, does not modify plasma corticosterone. At the same dose it was, furthermore, unable to prevent the adrenocortical stimulation induced by restraint stress.5. Brain amine content does not seem to play an important part in the control of corticotrophin releasing factor in corticotrophin secretion by the pituitary gland. The relationship between hypothalamic monoamines and other neurohumours is discussed.