Why we could all do with a siesta

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Public release date: 1-Jun-2006

http://www.eurekalert.org/pub_releases/2006-06/uom-wwc060106.php

Contact: Aeron Haworth

aeron.haworth@...

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University of Manchester

Why we could all do with a siesta

The Spaniards may have been right all along – a siesta after a hearty

lunch is natural, new research suggests.

Scientists at The University of Manchester have for the first time

uncovered how brain cells or 'neurons' that keep us alert become turned

off after we eat.

The findings – published in the scientific journal Neuron this week –

have implications for treating obesity and eating disorders as well as

understanding levels of consciousness.

" It has been known for a while that people and animals can become sleepy

and less active after a meal, but brain signals responsible for this

were poorly understood, " said Dr Denis Burdakov, the lead researcher

based in Manchester's Faculty of Life Sciences.

" We have pinpointed how glucose – the sugar in food – can stop brain

cells from producing signals that keep us awake.

Dr Burdakov's research has shown exactly how glucose blocks or

'inhibits' neurons that make orexins – tiny proteins that are vital for

normal regulation of our state of consciousness.

" These cells are critical for responding to the ever-changing

body-energy state with finely orchestrated changes in arousal, food

seeking, hormone release and metabolic rate to ensure that the brain

always has adequate glucose. "

Malfunction of orexin neurons can lead to narcolepsy, where sufferers

cannot stay awake, and obesity; there is also evidence that orexin

neurons play a role in learning, reward-seeking and addiction.

" We have identified the pore in the membrane of orexin-producing cells

that is responsible for the inhibiting effect of glucose.

" This previously unknown mechanism is so sensitive it can detect minute

changes in glucose levels – the type that occurs between meals for example.

" This may well provide an explanation for after-meal tiredness and why

it is difficult to sleep when hungry.

" Now we know how glucose stops orexin neurons 'firing', we have a better

understanding of what may occur in disorders of sleep and body weight.

" This research perhaps sheds light on why our European friends are so

fond of their siestas. "

--

ne Holden, MS, RD < fivestar@... >

" Ask the Parkinson Dietitian " http://www.parkinson.org/

" Eat well, stay well with Parkinson's disease "

" Parkinson's disease: Guidelines for Medical Nutrition Therapy "

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