More on darkness, serotonin, and circadium rhythm...
This week researchers report how serotonin decreases the body’s sensitivity to light and that exposure to constant darkness leads to a decrease in serotonin levels in the brain of fruit flies.
Remember, scientists study fruit flies alot because they provide the model system for examining "entrainment," the synchronization of the internal clock to the environment.
They say the findings suggest that serotonin may play a role in maintaining circadian rhythm, as well as modulating light-related disorders such as seasonal affective disorder (SAD).
The body’s 24-hour (circadian) clock controls cycles of wakefulness and sleep, as well as the rhythm of other physiological functions, such as body temperature and blood pressure. Although the body functions on roughly a 24-hour schedule, this cycle is capable of being reset by environmental disturbances.
Senior author Amita Sehgal, at Penn and a Howard Hughes Medical Institute Investigator, reports her findings in Neuron.
“In humans, a light pulse in the early evening delays rhythm-if it stays light later, you stay up later,” says Sehgal. “Disturbances in the late evening advance the body clock-an early dawn leads to an early rise. You do not want your clock to be so supersensitive to light that small fluctuations are going to throw it out of whack. Serotonin appears to modulate the response of the body clock to light.”
There is no doubt about serotonin being a good thing!