Researchers Suggest Possible Cause for Narcolepsy

Researchers Suggest Possible Cause for Narcolepsy

More than a decade ago, in the year 2000, researchers at the Sleep Research Center, from UCLA (University of California, Los Angeles), revealed that patients suffering from narcolepsy had almost 90% less neuropeptide hypocretin producing nervous cells, when compared to healthy patients. Narcolepsy is a neurological disorder that causes excessive sleepiness and uncontrollable periods of daytime sleep. The brain of narcoleptic patients is unable to control their circadian rhythm and clock. Another symptom that is common with narcoleptic patients is cataplexy, a sudden loss of muscle tone that causes patients to fall. Thought to affect approximately 3 million people worldwide, narcolepsy is still a disease without a cure.

The research from UCLA was the first study to have revealed a possible cause for narcolepsy. Following studies conducted by the same research team revealed that hypocretin is a chemical compound responsible for elevating alertness levels and mood. According to the studies, the death of cells called hypocretin cells, could be a possible cause of narcolepsy. However, their assumptions weren’t proven. Their newest study, published in the journal Annals of Neurology, reveals that an increased number of histamine-containing cells found in the brain could be the cause of death for the hypocretin cells.

Professor Jerome Siegel, one of the leaders of the study, reports that patients suffering from narcolepsy have approximately 65% more histamine-containing cells, when compared to healthy patients. The study suggests that the high number of histamine-containing cells is responsible for the loss of hypocretin-containing cells in patients suffering from narcolepsy. Histamine is a chemical molecule involved in the immune system. It is responsible for causing allergies in many patients with defective immune systems. However, histamine is also present in a type of cell found in the brain.

In their study, scientists examined the brains of 5 narcoleptic and 7 healthy brains taken from human cadavers. All 5 patients suffering from narcolepsy were diagnosed, prior to their death, as narcolepsy with cataplexy. Both dog and mouse models were examined in this study. The research team discovered that the brains taken from narcoleptic patients contained approximately 65% more histamine neurons that the brains of healthy patients. However, this observation wasn’t the same for the animal models.

Professor Siegel reports that even though both humans and animals with narcolepsy suffer from the same symptoms, it seems as the amount of histamine-containing cells found in the brains of narcoleptic animals remained unchanged. According to precedent studies, narcolepsy in animals is caused by a genetic mutation that blocks the function of hypocretin. However, until now, the cause of narcolepsy in humans was unknown.

“Our current findings indicate that the increase of histamine cells that we see in human narcolepsy may cause the loss of hypocretin cells”, affirmed professor Siegel. Furthermore, Siegel explains that the study might lead to further understanding of the brain’s plasticity and neurogenesis.