Dopamine neurons may regulate our biological clock

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hand switching off lightSwitching off and going to sleep may be more difficult if we are engaged in a pleasurable activity, suggests new research.

Researchers have identified some of the brain cells that control our body’s internal clock. The findings provide new insights into how the human body responds to jet lag, as well as into why it is so difficult to switch off your favorite show and go to sleep.

A team of researchers from the University of Virginia (UVA) in Charlottesville set out to examine the neurological underpinnings of our so-called body clock.

The phrase “biological clock” refers to the “center” that controls the different groups of interacting molecules that are found throughout the human body.

These different groups are controlled by a main “master clock” consisting of neurons located in an area of the brain called the suprachiasmatic nucleus (SCN). The SCN is found in the brain’s hypothalamus, and it consists of more than 20,000 neurons.

The new research identifies additional neurons that play a key role in regulating our bodily rhythms. Specifically, the new study – published in the journal Current Biology – finds that dopamine-producing neurons have a direct connection to the brain’s SCN.

Dopamine is a neurotransmitter that controls pleasure signaling, learning, and movement. It also helps the brain to process rewards, as well as to detect when food or a sexual partner is available.

Although it has deep biological roots, the activity of the body clock is also regulated by external stimuli, such as light and darkness.

The new findings may help researchers to better understand how phenomena such as jet lag or shift work affect the body, and to come up with better therapies for these effects.

The study was led by Ryan Grippo, a Ph.D. candidate and student of Ali Deniz Güler, a UVA professor of biology and neuroscience whose laboratory hosted the study.

Studying dopamine signaling in mice

Grippo and team examined two groups of mice.

One group was genetically modified to have a disrupted dopamine circuit, and the other group was kept as a normal control group.

More specifically, the first group of mice had the dopamine receptor signaling within the SCN genetically knocked off – that is, there was no communication between dopamine neurons in the brain’s so-called ventral tegmental area (VTA) and the SCN.

Next, the researchers altered the light schedules of the two groups of mice by 6 hours, recreating the conditions of jet lag.

The genetically modified group of mice was much slower to adapt to the schedule shift compared with its control counterparts. This indicated to the researchers that dopamine signaling between the VTA and the SCN is necessary for circadian rhythm regulation.

Because of dopamine’s role in processing rewards, these findings offer unique insights into how our body clock works.

This shows that when we engage in rewarding activities like eating, we are inadvertently affecting our biological rhythms […]. We may have found the missing link to how pleasurable things and the circadian system influence one another.”

Prof. Ali Deniz Güler

In other words, the new study may help to explain why it seems particularly difficult to go to bed early when we are watching our favorite TV show.

Prof. Güler further comments on the significance of the findings, saying:

“Scientists have been working for decades to help the body’s circadian system readily re-synchronize to variable work and eating schedules and flights across multiple time zones.”

“Finding this connection between dopamine-producing neurons and the circadian center allows us to target these neurons with therapies that could potentially provide relief of symptoms for travelers and shift workers particularly, and possibly people with insomnia,” he adds.

Prof. Güler is hopeful that the findings will lead to the “development of unique drugs, targeting specific neurons.”

“New understanding of dopamine-producing neurons and the connection to the body’s biorhythms may go a long way toward treatments to alleviate the harmful effects of these serious pathologies,” the researcher adds.

August 7, 2017 at 04:15AM

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