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A research team led by Nagoya University in Japan has discovered a new neural pathway connecting the body clock, stress and wakefulness in mammals.
The team identified a nerve cell, called cortical directed release hormones (CRF), which is a polypeptide hormone and neurotransmitter involved in the stress response, which becomes overactive when mammals are under stress, which can result in insomnia and other sleep disorders.
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The results of the Japanese team were recently published in the journal Science Advances.
Living things show a 24-hour oscillation, called a circadian rhythm. In mammals, the central circadian clock, found in suprachiasmatic nucleus (SCN) neurons, regulates the sleep-wake cycle.
However, in the case of life-threatening situations, the circadian rhythm signal is turned off to keep the animal awake so that it can escape danger even when it is usually bedtime.
And although interrupting the sleep-wake cycle is essential for survival, excessive or prolonged stress caused by such dangers can lead to insomnia and other sleep disturbances.
“It is well known that the body clock and stress have an effect on sleep, but it is not known which nerve pathway is needed to regulate the circadian rhythm of sleep and wakefulness,” said Dr Daisuke Ono from Nagoya University’s Environmental Medicine Research Institute. To determine the path, a Nagoya University research team led by Professor Akihiro Yamanaka and Dr Ono, together with Takashi Sugiyama of the Olympus Corporation in Japan, conducted a study in mice.
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The researchers focused on the cortex-directed hormone releasing hormone (CRF) neurons, which is known to play a role in the stress response, found in the paraventricular nucleus of the hypothalamus. They studied how sleep and wakefulness in mice were affected when these neurons were activated.
The results showed that active CRF neurons kept the animals awake and made them move vigorously, indicating increased vigilance. The researchers also noted that CRF neurons remained active when mice were awake, and when neuronal activity was suppressed, the animals’ alertness and motor activities decreased.
Other research has also shown that inhibitory neurons in the suprachiasmatic nucleus, called GABAergic neurons, play an important role in regulating the activity of CRF neurons, and that activation of these neurons stimulates orexin cells in the hypothalamus. lateral. , Which leads to increased vigilance.
Thus, the team concluded that GABAergic neurons in the suprachiasmatic nucleus control the activity of corticotropin releasing factor neurons, which ultimately regulate the sleep-wake cycle.
“We have identified this neural pathway in mice, which are nocturnal animals,” says Dr. Ono. “More studies are needed to clarify how the difference in night and day is regulated in the brain.”
“In today’s society, sleep disorders are a serious problem. We hope that our findings will contribute to the development of new treatments for insomnia and other sleep disorders caused by stress or circadian rhythm disorders.” , he added.
Source: medicalxpress
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