Histamine key to waking, study finds

WASHINGTON - Brain cells that contain the chemical histamine are critical for waking, scientists say in a study that sheds light on conditions such as narcolepsy.

Their finding, published in Neuron, also helps explain why antihistamines make many people sleepy.

"Our findings greatly improve our understanding of the brain activity responsible for maintaining consciousness and muscle tone while awake," said Jerome Siegel, of the University of California Los Angeles Neuropsychiatric Institute, who led the study.

"The findings should aid in the development of drugs to induce sleep and to increase alertness," said Dr Siegel.

The study is helping shed light on conditions such as narcolepsy, a sleep disorder marked by uncontrollable periods of sleep that often come on suddenly, as well as bouts of muscle weakness called cataplexy. It affects one in 200,000 people.

Working with narcoleptic dogs, his team earlier had found that brain cells that produce noradrenaline and serotonin shut off during the paralysis that marks cataplexy. But during cataplexy, histamine-producing neurons are normal.

"We hypothesise that the activity of histamine cells is linked to the maintenance of waking," they wrote.

- REUTERS