By a combination of biochemical and pharmacodynamical analyses the author conducted a differentiated study of the role of separate neurohormones (adrenalin, noradrenalin, dopamine, serotonine) and their interconnection with other regulating systems (corticosteroids, nucleic acids) in the neurochemical structure of experimental models in depressive behaviour (reserpine depressions, depressions due to inhibitors of dopamine-beta-oxydase). In the aspect of the author's concept concerning reciprocity of relationships between the central and peripheral catecholamine mechanisms on the basis of the obtained experimental data, their comparison with the previous clinico-biochemical investigations and literary data is considered to be the pathochemical basis of depression. This is considered to be a multicomponent structure of pathologically fixed changes of the central noradrenergic activity, relationships in the catecholaminergic system (hypothalamus--medullau substance of the adrenal glands) and processes of reswitching catecholamine influences on the state of other neurochemical regulatory systems.