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To Sleep, Perchance to Heal
| Article
# : |
19125 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
1 / 1991 |
2,876 Words |
| Author
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Richard Brown
Richard Brown is lecturer in psychology at the University of
Newcastle, New South Wales, Australia. His research interests
lie in the field of sleep and the immune response. |
Why do we sleep? Why are we compelled to spend almost one-third of our lives doing what at first glance appears to be nothing? Sleep dominates every aspect of our existence. We organize every activity with regard to our need for sleep. But despite this dominance of sleep over our daily lives, the purpose of sleep remains a mystery. Some recent observations in the seemingly disparate fields of immunology and sleep research, however, offer a clue that may help answer the question "Why do we sleep?"
The Bacteria Connection
At the beginning of this century, two Frenchmen, Rene Legendre and Henri Pieron, set out to verify the presence of sleep-inducing substances within the brain. An idea central to many sleep theories at that time was that sleep resulted from an accumulation of "poisons" within the body during the waking hours. Among the accused substances were lactic acid, carbon dioxide, and yes, even then, cholesterol. It was thought that during sleep some purgative mechanism was activated and these so-called toxins were removed from the system. Thus we awoke from sleep feeling refreshed and ready to take on the rigors of another day.
To isolate these supposed toxic byproducts of waking life, Legendre and Pieron deprived dogs of sleep for days at a time, then carefully extracted samples of the fluid surrounding their brains. They transferred this fluid to the nervous systems of dogs that had normal levels of sleep. The scientists watched as the recipient dogs, wide awake until the moment of injection, fell into a profound sleep. Legendre and Pieron deduced that this phenomenon was due to the presence of one or more substances within the cerebral fluid of the sleep-deprived dogs. This finding was evidence that sleep had a molecular basis and that these molecules apparently accumulated within the nervous system over the period of the waking day. Legendre and Pieron dubbed their substance "hypnotoxin".
While the toxin theory of sleep later fell by the wayside, the Pieron phenomenon, as it became known, still required an explanation. Sporadic attention was paid to the phenomenon over the years of this century until, in the 1960s, a Harvard group led by Dr. John Pappenheimer began the first contemporary attempt to isolate the mysterious hypnotoxin. The team successfully replicated the original studies of Legendre and Pieron using concentrated extracts from the brain and spinal fluid of sleep-deprived goats and then attempted to identify the substance or substances responsible. This is where the story took a fascinating
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