Researchers at the University of California, San Diego have found neurons in the mouse brain that respond to seasonal changes in daylight hours. The study was published in the journal Science Advances.
Inside the hypothalamus of the human brain is a small structure called the suprachiasmatic nucleus (SCN), where neurons regulate the body’s response to circadian rhythms. The study’s authors found that in mice whose brains work similarly to that of a human, neurons in the SCN changed the expression of important neurotransmitters. These substances transmit electrochemical impulses from one neuron to another. Changing the functioning of neurons led to restructuring of the behavior and physiology of the mice.
The scientists also showed that seasonal changes in lighting affect the number of neurons that release neurotransmitters in the paraventricular nucleus, an area of the brain that plays an important role in controlling stress, metabolism, growth, reproduction and other autonomic functions.
In addition, the scientists found that it is possible to artificially manipulate the activity of certain SCN neurons and induce dopamine expression in the paraventricular nucleus.
These two regions of the brain represent a promising target for new treatments for psychiatric disorders associated with seasonal changes in lighting. The most common condition is seasonal affective disorder, a type of depression associated with less exposure to natural sunlight during the winter months.