by J. Travis Since that discovery, adenosine has begun to
intrigue more and more sleep investigators. Many studies in
animals have shown that blocking adenosine's actions in the
brain increases alertness, while injections of adenosine or
similar compounds induce apparently normal sleep. Now, by
monitoring the brain chemistry of cats, a team of researchers
has shown that natural adenosine concentrations in at least some
parts of the brain build up during waking periods and decline
during sleep. Moreover, the investigators report in the May 23
Science, adenosine concentrations in the brain shoot up
dramatically in animals forced to stay awake. The findings offer
the most compelling evidence yet that adenosine is one of the
long-sought factors whose fluctuating concentrations in the
brain determine when an animal must sleep. "That's fantastic. We
predicted what they got," says Miodrag Radulovacki of the
University of Illinois College of Medicine in Chicago, the
earliest champion of the adenosine theory of sleep.