Orexin, also known as hypocretin, is a neuropeptide that regulates wakefulness, appetite, and addiction. This molecule has two names because it was discovered by two independent groups of researchers at around the same time. When referring to the gene that codes for this neuropeptide, scientists use the name “hypocretin”. When talking about the peptide, the name “orexin” is used. This peptide is highly conserved in humans, rats, and other vertebrates. Both of the research groups were working with rodents when they discovered orexin, yet its function stays the same in humans.
Narcolepsy and Orexin
One of the most obvious signs of a lack of orexin is the inability to stay awake. Narcolepsy is the name of this disorder and it happens when the cells that produce orexin die off. This is considered an autoimmune disorder because a gene mutation in the T-cell receptor causes the immune system to attack and kill the orexin producing cells. People and animals with narcolepsy experience extensive daytime sleepiness, transition quickly between sleeping and waking, and lose muscle tone when they experience something very happy.
Narcolepsy is treated with a drug called Modafinil. This drug stimulates a host of wakefulness centers in the brain, including the orexin system. Other systems include the histamine, dopamine, and serotonin systems. Narcolepsy aside, Modafinil is used by nighttime workers or soldiers who need to stay away for long periods of time. As you can imagine, the person experiences prolonged periods of not just wakefulness, but also concentration. Once the drug wears off, they will start to feel sleepy again.
Addiction and Appetite
Orexin plays a role in regulating appetite and also in addiction. Studies showed that orexin increased cravings for food. It can also make you eat more because it stops the feedback message from your gut that you’re full. As for addiction, scientists found that if you block orexin receptors, mice lose interest in alcohol, even though the drug was fully accessible to them.
Get Your Own Orexin
This super conserved molecule is so important in regulating the lives, metabolisms, and sanity of so many vertebrates, we thought it deserved its own piece in our science jewelry collection. Purchase it for yourself or for a friend. This necklace makes a great gift for those living with a sleep disorder, those fighting to improve the quality of life of those with said sleep disorder, or to those studying into the long, lonely night (aka sleepy but starry-eyed, pre-med students).Remember, shipping is always free!
written by Science with Evie