Alzheimer's Disease Possibly Linked To Sleep Deprivation

sonnejw0 writes "NewScientist is reporting a link between sleep deprivation and Alzheimer's Disease via an increased amyloid-beta plaque load thought responsible for a large part of the symptoms of the disease, in mice. Medication to abrogate insomnia reduced the plaque load. Also discussed is a recently discovered sleep cycle of amyloid-beta deposition in the brain, in which levels decrease while asleep. 'Holtzman also tried sending the mice to sleep with a drug that is being trialled for insomnia, called Almorexant. This reduced the amount of plaque-forming protein. He suggests that sleeping for longer could limit the formation of plaques, and perhaps block it altogether.'"

Re:Why do we sleep?

[bill_mcgonigle]

Could delaying the inevitable onset of Alzheimer's be the biological function of sleep? Last I heard, the purpose of sleep wasn't entirely clear

What? No. There are at least two functions of sleep that I know of: one is cleaning up misshapen proteins that accumulate during the day (and may be what causes tiredness). The other is transcription of short-term memory into long-term memory. Evolutionarily speaking, nobody ever lived long enough to get Alzheimers. Those who did wandered off into the tundra and didn't burden the tribe any longer.

Re:As a graduate student...

[fuzzyfuzzyfungus]

Don't laugh, college boy... [bmj.com]

Re:But... But... But...

[sonnejw0]

Caffiene helps by dilating blood vessels, supplying the brain with more oxygen, glucose, and most importantly the removal of toxic reactive oxygen species. At least that's what I thought.

Re:Why do we sleep?

[demonlapin]

Well, the Schedule II rating is a very easy way to quit getting prescribed. Amphetamines work, and they're cheap. But you *can* get high with them, so we have to restrict the crap out of them. [Insert drug war rant.]

OTOH, they're not without downsides. See, amphetamines work by increasing the catecholamine (particularly norepinephrine) levels in the brain. They push the catecholamines out of the storage vesicles into the synapses. (FWIW, cocaine works by preventing neurotransmitters from being absorbed back into the neuron that released them - it doesn't change the amount released.) So, after a few days straight of amphetamine use, you crash HARD - you no longer have any catecholamines, so you can't stay awake. A pharmacist friend of mine told me of a story told by some of her professors who had trained in the 50s, when amphetamines were either OTC or just plain prescription (not scheduled). Guys would keel over in the middle of final exams because they had been awake for 3 straight days, finally ran out of norepi, and couldn't stay awake. No solution for it but to let them have 12-24 hours to synthesize more.

Re:Implications for other Mental Diseases?

[demonlapin]

No. Antipsychotics are generally dopamine receptor blockers. While this does produce sedation (and weight gain), they are not sleeping pills. Interestingly enough, the first antipsychotics to be discovered were found by projects that were trying to find antihistamines, which were sedative because they were (accidentally) also anticholinergics;

Re:Implications for other Mental Diseases?

[demonlapin]

I'm a practicing physician with a strong interest in pharmacology. I do know the technical details. Unfortunately, I apparently suck at making a point, because this is the second comment in this thread that I've had fall victim to my unclear phrasing.

To amplify: They are sedative, but they are most assuredly not glorified sleeping pills - a benzodiazepine, a barbiturate, or a central anticholinergic would be what people think of as sleeping pills, and none of those would work.

They act as "mood stabilizers", a property discovered early on (Thorazine, for example, was advertised as useful for calming the "agitated senile" patient.) This, not their sedative effect, is why they're useful for psychosis and psychiatric illness. The sedation is unfortunate but unavoidable - many, many schizophrenics won't take antipsychotics because they can't stand the feeling of being so mentally slowed.