[Inhibition of monoamineoxidase and day-night-rhythm: correlation of physiological and biochemical parameters (author's transl)].

The motor activity of rats following medication with monoamine-oxidase inhibitors was registered continuously over a period of nine days. At the same time the enzyme activity of monoamineoxidase (MAO) form A and B and the concentration of serotonin, tryptophan, 5-hydroxyindolacetic acid and norepinephrine were measured in brain stem and hippocampi. We draw the following conclusions: 1. The rhythmic changes in the levels of serotonin and norepinephrine play a minor role in the circadian rhythm. 2. MAO-inhibitors influence the timing mechanism. A relationship between this finding and the therapeutic effect on depressed patients is discussed. 3 Dopaminergic neurons antagonize the activation by adrenergic neurons during the dark-period.