According to the researchers, the length of the day affects the brain’s opioid mediators that regulate mood and sociality.
Seasons affect emotions and social life. Negative emotions subside in the summer, and during the dark months of winter, anxiety disorder, which varies from season to season, is most common.
Researchers at the Turku PET Center showed in a recent study how the season affects brain function.
The length of the day affects the opioid neurotransmitters in the brain, whose activity regulates both mood and sociality.
In the study compared the effect of day length on neurotransmitter activity in both humans and rats. According to the study, the number of light hours per day affects the receptors that regulate brain opioid function.
Postdoctoral researcher at the Turku PET Center Lihua Sunin according to the researchers, their study found that the number of opioid receptors depended on the time of year the imaging study had been done.
“The strongest changes were observed in the areas that regulate emotions and sociality in the brain. This seasonal variation in opioid activity may be an important factor in explaining seasonal mood swings, ”says Lihua Sun of the University of Turku. in the bulletin.
The PET Center is a joint research center of the University of Turku, Åbo Akademi University and Turku University Central Hospital.
The study involved 204 volunteers. A small amount of a radioactive tracer that binds to the opioid receptors in the brain was administered into their bloodstream. Degradation of tracers was measured with a PET camera.
The study was performed using positron emission tomography (PET). PET is a sectional imaging method that provides information about, for example, tissue function. It is a useful method for examining, for example, the brain, heart or the prevalence of cancer.
Researchers wanted to confirm the significance of light in animal research as well: whether changes in brain function are caused by the amount of light or some other factor.
To clarify the issue, the researchers measured the brain neurotransmitter activity when the animals were kept under standard conditions and only the duration of daylight was changed.
The results obtained in rat experiments were similar to those in human studies.
“Based on the results, the amount of daylight in particular is a critical factor for the seasonal variation of opioid mediators. The results help to understand the brain mechanisms behind the seasonal variation in mood, ”says the professor. Lauri Nummenmaa From the PET Center.
The study is based on the large brain database of Tyks and the PET Center, which compiles different types of brain images for extensive analysis. The results were published in The Journal of Neuroscience.