From: Eugene.Leitl@lrz.uni-muenchen.de
Date: Tue Feb 06 2001 - 13:48:19 MST
-------- Original Message --------
From: Larry Klaes <lklaes@bbn.com>
Subject: [>Htech] New Brookhaven Lab Study Shows How Ritalin Works
To: "Also transhumantech-l@excelsior.org" <transhumantech@yahoogroups.com>
CC: META@egroups.com
Date: Tue, 16 Jan 2001 15:29:23 -0500
Reply-To: pubaf@bnl.gov
Sender: owner-bnl-announce-l@bnl.gov
From: BNL Media & Communications <pubaf@bnl.gov>
To: bnl-announce-l@bnl.gov
Subject: New Brookhaven Lab Study Shows How Ritalin Works
The following news release is being issued today by Brookhaven
National Laboratory.
***
FOR IMMEDIATE RELEASE
January 16, 2001
Contact: Peter Genzer, 631 344 3174, or
Mona S. Rowe, 631 344 5056
New Brookhaven Lab Study Shows How Ritalin Works
UPTON, NY - New research on Ritalin, a drug prescribed to millions of
American children each year with Attention Deficit Hyperactivity
Disorder (ADHD), shows for the first time how the drug acts in the
human brain and why it is so effective.
The findings are reported in the January 15 issue of the Journal of
Neuroscience by researchers from the U.S. Department of Energy's
Brookhaven National Laboratory. The publication can be found on the
Web at
http://www.jneurosci.org/cgi/content/full/20014896
Although Ritalin has been used for more than 40 years as a successful
treatment for ADHD, minimal information has been gathered to date on
exactly how the drug works in the brain, outside of limited animal
studies. This latest study, on humans, indicates that Ritalin
significantly increases levels of dopamine in the brain, thereby
stimulating attention and motivational circuits that enhance one's
ability to focus and complete tasks.
"For the first time, we are seeing that Ritalin given at doses
commonly used to treat children with ADHD significantly increases
levels of dopamine in the brain," said psychiatrist Nora Volkow, head
of the research team and Associate Laboratory Director for Life
Sciences at Brookhaven Lab. "This combination - the ability to
increase motivation and also directly activate circuits of attention
- is likely to be key to the beneficial effects of Ritalin."
Earlier animal and limited human studies had indicated that Ritalin
interferes with the recycling of dopamine within the brain by
blocking dopamine transporters. However, since these earlier studies
involved injection of much higher doses of Ritalin, it was unclear
whether the drug would increase extracellular dopamine at doses used
therapeutically for children.
Using a technique called positron emission tomography, or PET,
researchers at Brookhaven's Center for Imaging and Neurosciences
studied dopamine levels in 11 male subjects. In two sessions, the
volunteers were each given a dose of Ritalin, calculated using their
body weight to correspond to the doses given to children with ADHD,
or a placebo. While their brains were scanned to record dopamine
levels, the subjects were asked to rate their feeling of restlessness
and "high." Meanwhile, physicians monitored each subject's blood
pressure and heart rate.
The results showed that brain dopamine levels increased significantly
approximately 60 minutes following ingestion of the drug as compared
to the placebo. "We now know that by increasing the levels of
extracellular dopamine, you can activate these motivational circuits
and make the tasks that children are performing seem much more
exciting," said Volkow. "By raising that level of interest, you can
significantly increase the ability of the child to focus on the task."
Volkow added that Ritalin also works to suppress "background" firing
of neurons not associated with task performance, allowing the brain
to transmit a clearer signal. "Random activation of other cells can
distract you, and children with ADHD are easily distracted," she
said. "Ritalin suppresses that background firing and accentuates the
specific activation, basically increasing the signal-to-noise ratio
and increasing a child's ability to focus."
Volkow is now planning a follow-up study of subjects suffering from
ADHD. "We hypothesize that we will find that ADHD sufferers have
decreased function of dopamine circuits and are therefore easily
distracted," she said. "The effect of Ritalin should be to normalize
these levels, allowing them to focus and pay attention."
The findings also have important implications for another research
area - understanding why Ritalin, which is chemically quite similar
to highly addictive cocaine, is not addictive when taken in pill
form. One thing in common with all drugs of abuse is that they
increase dopamine levels. Since oral doses of Ritalin do not produce
a "high," the Brookhaven researchers did not expect to see a
significant increase in dopamine levels. Since they did see a
significant increase, Volkow postulates that another factor is at
work.
"We've found that for drugs of abuse to be effective, they must get
into the brain very quickly, and for that reason, when injected,
Ritalin can become addictive," she said. "However, when Ritalin is
given in pill form it takes at least 60 minutes to raise dopamine
levels in the brain. So, it is the speed at which you increase
dopamine that appears to be a key element in the addiction process."
The study's authors also included Gene-Jack Wang, Laurence Maynard,
Samuel Gatley, Andrew Gifford, and Dinko Franceschi of Brookhaven's
Medical Department, and Joanna Fowler, Jean Logan, Madina Gerasimov,
and Yu-Shin Ding of Brookhaven's Chemistry Department.
The research was funded by DOE's Office of Energy Research and by the
National Institute on Drug Abuse, part of the National Institutes of
Health.
The U.S. Department of Energy's Brookhaven National Laboratory
creates and operates major facilities available to university,
industrial and government personnel for basic and applied research in
the physical, biomedical and environmental sciences, and in selected
energy technologies. The Laboratory is operated by Brookhaven
Science Associates, a not-for -profit research management company,
under contract with the U.S. Department of Energy.
-30-
* * *
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