Neurotransmitter reverses sleep deprivation

By Karla Gale

NEW YORK (Reuters Health) - Administration of orexin-A, a naturally occurring brain neurotransmitter, counteracts the intellectual deficits and altered brain metabolism induced by sleep deprivation in monkeys, new research findings show.

Orexin-A was tested because of its know specific brain activity in controlling sleep processes in mammals, lead author Dr. Sam A. Deadwyler told Reuters Health.

Orexin-A is released by neurons in the brain, the scientists explain in the Journal of Neuroscience, and orexin-A receptors are located on neurons in many brain regions affected by sleep and sleep deprivation.

Deadwyler, a neurobiologist at Wake Forest University in Winston-Salem, North Carolina, and his team worked with eight monkeys trained to perform an intellectual task to test short-term memory.

The effect of orexin-A on the animals' performance was analyzed after a normal 12-hour sleep cycle and after being kept awake for 30 to 36 continuous hours. Brain metabolism was evaluated by F18-fluorodeoxyglucose PET scanning.

When the monkeys were alert, orexin-A did not improve test performance. In fact, at the highest concentration of orexin-A, intellectual functioning worsened.

However, when the monkeys were deprived of sleep, a low- or high-dose of orexin-A significantly improved the animals' test performance.

It was even more potent when it was administered through the nose. Cognitive performance was restored to normal alert levels, and nasal orexin-A improved performance on more difficult tests.