Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mood Lighting: Penn Researchers Determine Role of Serotonin in Modulating Circadian Rhythm

11.07.2005


Researchers at the University of Pennsylvania School of Medicine have determined 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. These 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). Senior author Amita Sehgal, PhD, Professor of Neuroscience at Penn and a Howard Hughes Medical Institute (HHMI) Investigator, and colleagues report their findings in the July 7 issue of Neuron.



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. In Sehgal’s lab, fruit flies provide the model system for examining entrainment, the synchronization of the internal clock to the environment.

“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.”


Entrainment was tested in flies by exposing them to a pulse of light during the dark period. Closely resembling the body clock adjustment seen in humans, Sehgal’s flies reset their body clock following the “night-time” disturbances. However, this adjustment was lessened when the flies were treated with serotonin prior to the test.

Sehgal speculates that serotonin is acting to protect the body clock from being over-responsive to light disturbances. “You do not want your clock to be so supersensitive to light that small fluctuations are going to throw it out of whack,” she explains. “Serotonin appears to modulate the response of the body clock to light.”

In flies, a protein called cryptochrome drives the response of the body clock to light. Under normal circumstances, light excites cryptochrome located within the brain, which in turn, interacts directly with the clock protein to reset the clock. Sehgal and colleagues discovered that serotonin works by attaching to the serotonin 1B receptor, altering the activity of another protein, GSK3bß, which further changes the cascade of events leading to the resetting of the clock.

Sehgal points to the clinical implications for understanding the interaction between GSK3ß and serotonin. Lithium, a drug commonly prescribed to treat bipolar disorder, targets GSK3ß. “Lithium resets the clock in all organisms that have been examined,” explains Sehgal. “Assuming that the mechanism works the same way for mammals, the implication would be that antidepressants other than Lithium can also affect the clock.”

Sehgal and colleagues also studied the role of serotonin in dark adaptation, the experience of increased sensitivity to light following long periods of darkness. After seven days in constant darkness, flies demonstrated significantly reduced levels of serotonin compared to flies exposed to the normal light-dark cycle. Interpreting the relationship of serotonin as it influences circadian rhythm, Sehgal suggests, “In situations of dark adaptation, you may become more sensitive to light because serotonin goes down.”

The reduction of serotonin levels in flies kept in constant darkness may provide scientists with insight into the etiology and treatment of SAD, a mood disorder related to reduced sunlight during winter. “People with seasonal affective disorder will respond to medications such as Prozac to increase serotonin,” says Sehgal. “Patients also respond to light therapy. We now believe that light is also increasing serotonin-perhaps this is why both of these treatments are effective.”

By identifying the mechanism of interaction between serotonin and the body clock, as well as the environmental factors influencing the levels of serotonin in the brain, Sehgal and colleagues hope to be able to shed light on the possible role of circadian activity on affective disorders. The interplay of serotonin, light, and the circadian system suggests a close relationship between circadian regulation and mental health.

Sehgal’s co-authors are Quan Yuan, Fangju Lin, and Xiang Zhong Zheng, all from Penn and HHMI. The research was funded by the Howard Hughes Medical Institute.

Karen Kreeger | EurekAlert!
Further information:
http://www.uphs.upenn.edu

More articles from Health and Medicine:

nachricht Investigators may unlock mystery of how staph cells dodge the body's immune system
22.09.2017 | Cedars-Sinai Medical Center

nachricht Monitoring the heart's mitochondria to predict cardiac arrest?
21.09.2017 | Boston Children's Hospital

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>