This release is available in French.
Lack of sleep is a common complaint but for many, falling asleep involuntarily during the day poses a very real and dangerous problem. A new study from the Montreal Neurological Institute (MNI) at McGill University demonstrates interestingly, that sleep-wake states are regulated by two different types of nerve cells (neurons), melanin-concentrating hormone (MCH) neurons and orexin (Orx) neurons, which occupy the same region of the brain but perform opposite functions. The MNI study is the first to discover that MCH neurons are activated during sleep and could thus be important in regulating the sleep state. The study, published in this week's issue of the journal Proceedings of the National Academy of Sciences (PNAS), provides deeper understanding of the sleep-wake cycle and vital insight into the basis of sleep disorders such as narcolepsy and possibly also other diseases such as depression and Parkinson's.
Sleep is regulated by processes in the brain in response to how long we are awake in addition to the light/dark cycle controlled by the circadian rhythm. With Drs. Oum Hassani and Maan Gee Lee, Dr. Barbara Jones at the MNI were studying a structure in the brain called the lateral hypothalamus (LH) known to be critical for maintaining wakefulness. MCH neurons, co-distributed with Orx neurons, constitute less than 10% of the LH. Previous studies have shown that Orx neurons are essential for maintenance of the awake state. These neurons are active in the waking state and turn off during sleep and in their absence, animals and humans experience narcolepsy with cataplexy or sudden loss of mucle tone. However, the role of MCH neurons was until now, unclear. Evidence from earlier knockout studies suggested that MCH neurons might play a different role than Orx neurons in regulating activity and slee
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