A new discovery by researchers from the University of Edinburgh could lead to the development of treatments such as eye drops that counter the effects of jet lag.
The team identified a type of signaling molecule that communicates light intensity information from the retinas in our eyes to our brain to help regulate the biological clock. The molecule could be a potential target for future therapies.
The suprachiasmatic nucleus (SCN) – which is made up of about 20,000 brain cells – acts as a biological clock and helps keep our circadian rhythms in check. Circadian rhythms influence body temperature, hormone release, and other biological “alerts” like needing to go to the bathroom or quench thirst. Long term effects of a disrupted circadian rhythm include increased weight gain, diabetes, cardiovascular disease, and may even contribute to a higher risk of cancer, depression and premature mortality.
The SCN resides within the hypothalamus region of the brain, and responds to information sent from the body’s eyes to “know” what biological time it is.
For example, bright light in the early morning hours triggers cells in the retina known as ganglion cells to tell the SCN to activate genes that prompt us to wake up.
Until now, it was unclear how exactly the ganglion cells relayed proper information to the brain.
The new study, published in the Journal of Physiology, found that retinal ganglion cells produce molecules called vasopressin, which act as the messengers from the eyes to the brain to help regulate the biological clock.
Through a series of experiments in rats, the researchers found that bright pulses of light triggered the retinal ganglion cells in the rats’ eyes to release vasopressin. They also observed the neurons in the brain’s SCN activate as a result of the light pulses.
However, when the team injected a compound into the brains of the rats that blocked vasopressin, the brain cells did not respond as well to the pulses of light.
Traveling into different time zones and being exposed to light intensity the body is not used to at certain times of the day alters the circadian rhythm and leads to jet lag.
The research team believes that with additional research, eye drops or other pharmaceutical treatments could be developed to adjust the levels of vasopressin coming from the eye to help reset the biological clock and allow people to recover much faster from jet lag.
“Our exciting results show a potentially new pharmacological route to manipulate our internal biological clocks. Studies in the future that alter vasopressin signaling through the eye could lead to developing eye drops to get rid of jet lag, although we are still a long way off from this,” said Mike Ludwig, of the Centre for Integrative Physiology at the University of Edinburgh.