Narcolepsy is a disorder in which a person goes into uncontrollable periods of deep sleep. They can fall asleep without warning, anywhere and anytime. Past UCLA studies have shown that people who suffer from narcolepsy had 90 percent fewer neurons with the neuropeptide hypocretin in their brains than healthy people. Researchers then found that hypocretin, an arousing chemical, was responsible for keeping us awake and elevating our moods. They determined dying hypocretin cells were the cause of narcolepsy. But now, a new study suggests another brain cell is responsible for the disorder as well: histamine.

Histamine is an immune system chemical in the body that kills invading cells. While it can cause allergy symptoms by attacking cells in a person's nose, eyes, throat, etc., it can also be found in a type of brain cell.

Researchers examined five narcoleptic brains and seven normal brains from human cadavers. All narcoleptic brains were also cataplexic, a disorder that normally accompanies narcolepsy in which the body loses all muscle function causing them to collapse if standing. In addition to the human narcoleptic brains, mouse and dog brains were also examined.

All human narcoleptic brains had an average of 64 percent more histamine neurons when compared to the normal brains.

"Our current findings indicate that the increase of histamine cells that we see in human narcolepsy may cause the loss of hypocretin cells," Jerome Siegel, director of the Center for Sleep Research at the UCLA Semel Institute for Neuroscience and Human Behavior, said in a press release.

Interestingly, the animals with narcolepsy did not show any indication of increased histamine.

"Humans and animals with narcolepsy share the same symptoms, but we did not see the histamine cell changes we saw in humans in the animal models we examined," Siegel said. "We know that narcolepsy in the animal models is caused by engineered genetic changes that block hypocretin function. However, in humans, we did not know why the hypocretin cells die."

These findings also allude to neurogenesis - the brain's production of new neurons - performing other functions than just replacing dead neurons.

"This paper shows for the first time that neuronal numbers can increase greatly and not just serve as replacement cells," Siegel said. "In the current example, this appears to be pathological with the destruction of hypocretin, but in other circumstances, it may underlie recovery and learning and open new routes to treatment of a number of neurological disorders."

Source:

John J, Thannickal T, Siegel J, et al. Greatly increased numbers of histamine cells in human narcolepsy with cataplexy. Annals of Neurology. 2013.Narcolepsy is a disorder in which a person goes into uncontrollable periods of deep sleep. They can fall asleep without warning, anywhere and anytime. Past UCLA studies have shown that people who suffer from narcolepsy had 90 percent fewer neurons with the neuropeptide hypocretin in their brains than healthy people. Researchers then found that hypocretin, an arousing chemical, was responsible for keeping us awake and elevating our moods. They determined dying hypocretin cells were the cause of narcolepsy. But now, a new study suggests another brain cell is responsible for the disorder as well: histamine.

Histamine is an immune system chemical in the body that kills invading cells. While it can cause allergy symptoms by attacking cells in a person's nose, eyes, throat, etc., it can also be found in a type of brain cell.

Researchers examined five narcoleptic brains and seven normal brains from human cadavers. All narcoleptic brains were also cataplexic, a disorder that normally accompanies narcolepsy in which the body loses all muscle function causing them to collapse if standing. In addition to the human narcoleptic brains, mouse and dog brains were also examined.

All human narcoleptic brains had an average of 64 percent more histamine neurons when compared to the normal brains.

"Our current findings indicate that the increase of histamine cells that we see in human narcolepsy may cause the loss of hypocretin cells," Jerome Siegel, director of the Center for Sleep Research at the UCLA Semel Institute for Neuroscience and Human Behavior, said in a press release.

Interestingly, the animals with narcolepsy did not show any indication of increased histamine.

"Humans and animals with narcolepsy share the same symptoms, but we did not see the histamine cell changes we saw in humans in the animal models we examined," Siegel said. "We know that narcolepsy in the animal models is caused by engineered genetic changes that block hypocretin function. However, in humans, we did not know why the hypocretin cells die."

These findings also allude to neurogenesis - the brain's production of new neurons - performing other functions than just replacing dead neurons.

"This paper shows for the first time that neuronal numbers can increase greatly and not just serve as replacement cells," Siegel said. "In the current example, this appears to be pathological with the destruction of hypocretin, but in other circumstances, it may underlie recovery and learning and open new routes to treatment of a number of neurological disorders."

Source:

John J, Thannickal T, Siegel J, et al. Greatly increased numbers of histamine cells in human narcolepsy with cataplexy. Annals of Neurology. 2013.