While the occasional all-nighter to cram for exams or finish a grant proposal may seem like no big deal, chronic or frequent sleep deprivation could take its toll on brain health in later life, two new studies suggest. Based on microdialysis experiments in live mice, Dave Holtzman, Washington University, St. Louis, Missouri, and colleagues report in the current issue of Science that extracellular amyloid-beta levels in the brain fall during slumber and rise with wakefulness. They discovered that these amyloid-beta dynamics rely on the hormone orexin, and that forcing animals to sleep or stay awake decreases or increases amyloid-beta plaque formation accordingly in a mouse model for Alzheimer disease.

Earlier work from the Holtzman lab had shown that synaptic activity triggers amyloid-beta (Abeta) release, suggesting that the sleep-deprived mice in the current study churned out more Abeta because their brains were revved up longer than usual. While this is hard to prove formally, a rat electrophysiology study published in the September 24, 2009 issue of Neuron seems to lend support for that idea (Newswise).

For more details, see the report at the

Alzheimer Research Forum

References:

Kang J-E, et al. Amyloid-Beta Dynamics are Regulated by Orexin and the Sleep-Wake Cycle. Science 2009 Sept 24. Abstract

Vyazovskiy VV, et al. Cortical Firing and Sleep Homeostasis. Neuron 2009 Sept 24;(63):865-878. Abstract