[Seasonal and circadian changes in the serotonin content and metabolic rate in the brain of white mice].

A summary is given of the results of recent experiments on seasonal and circadian rhythms of serotonin content and of its metabolite, 5-hydroxyindolyl acetic acid, in the mouse brain. It has been ascertained that the content of serotonin reaches maximum in June and December, while its metabolism is also elevated in the summer months and December. The content of serotonin is higher in the day time, whereas its metabolism is activated during the dark period.