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For more information, contact Michelle Muth at 301-443-6245
RESEARCH NEWS
Study Finds That Methamphetamine Use Can Increase Stroke-Related Brain Damage
Researchers from the National Institute on Drug Abuse (NIDA) found that
methamphetamine use prior to stroke increases damage to the brain. Methamphetamine
appears to inhibit factors that occur naturally within the brain and that help protect it
from neuronal damage following trauma such as stroke or other injury.
NIDA researchers, joined by scientists from the Tri-Service General Hospital,
National Defense Medical Center, Taipei, Taiwan, used mice to ascertain the effects of
methamphetamine on the brain following stroke. The researchers pretreated mice with
either methamphetamine or a saline solution, temporarily blocked the blood flow through
the animals' right middle cerebral artery and bilateral carotid arteries (mimicking an
ischemic stroke), and observed the effects.
The researchers found more extensive brain damage in the mice pretreated with
methamphetamine than in those treated with the saline solution.
Dr. Yun Wang, head of the research team, says that their experiments found at least one
possible mechanism to explain this effect. They observed that methamphetamine pretreatment
decreased glial-cell-line-derived neurotrophic factor (GDNF) in the mice brain; when GDNF
was administered into the brains of the mice before their arteries were blocked, the effects
of methamphetamine-facilitated stroke were reduced.
This result, Dr. Wang says, indicates that methamphetamine may act to exacerbate
brain damage following stroke by inhibiting GDNF pathways.
- WHAT IT MEANS: Scientists knew that methamphetamine, an addictive stimulant
drug, increases heart rate and blood pressure and can cause irreversible damage
to blood vessels in the brain, resulting in strokes. This evidence that methamphetamine
can increase stroke-related damage to the brain further illustrates the danger of this drug.
The study, led by Dr. Yun Wang, appears in the March issue of Stroke. The paper is
posted on the journal's Web site at http://stroke.ahajournals.org/.
Study Examines Link Between Dopamine Receptor and Curtailing Cue-induced Craving for Cocaine
Cue-induced craving - seeing, hearing, or smelling something that triggers desire -
often prompts a former addict to resume drug use even after long periods of abstinence.
Recently, researchers at the Scripps Research Institute in La Jolla, California, used rats to
demonstrate that it may be possible to reduce cue-induced craving for cocaine by blocking
the dopamine receptor D1. Dopamine is a neurotransmitter that regulates feelings of pleasure,
and cocaine use increases the concentration of dopamine in the brain, resulting in the
"rush" cocaine users feel when using the drug.
"Better understanding of the biological basis of cue-induced craving and relapse has substantial potential
clinical benefit, including providing leads to the development of more effective medications and behavioral
interventions to treat addiction," says NIDA Director Dr. Alan I. Leshner.
The researchers trained 34 rats to self-administer cocaine by pressing a lever, accompanied by the sound
of a tone. Once the rats established stable levels of daily cocaine intake, investigators withheld the drug. When
the lever/tone cue no longer administered cocaine, the rats lost the learned behavior.
Four months later, the rats were again given access to cocaine using the lever/tone cue at intervals
immediately following behavior-extinction training. Once the lever/tone cue again signaled cocaine availability,
the rats quickly resumed pressing the lever in an attempt to take the drug.
During this study, scientists pinpointed the regions of the rat brain that may be involved in the motivating
effects of drug cues. The D1 antagonist treatment not only reversed drug-seeking behavior induced by the
cocaine cues, but concurrently reversed the neural activation.
- WHAT IT MEANS: These observations support the hypothesis that learned responses to drug-related
behavior are important in long-lasting vulnerability to relapse to drug use and help explain the
neurobiological basis for this vulnerability.
This study, led by Dr. Friedbert Weiss, appeared in the February 13, 2001, issue of PNAS: Proceedings of the
National Academy of Sciences. An abstract and other information about the article is available at http://www.pnas.org.
Nicotine Causes Degeneration in Brain's "Weak Link" for Addictive Drugs
Researchers at the University of California, Los Angeles (UCLA), have found that, in rats, continuous doses
of nicotine cause degeneration of brain cells in the fasciculus retroflexus (FR), a bundle of nerve cells that acts
as a pathway between limbic forebrain regions and the midbrain. Previous research established that one half
of FRÔs two parts is damaged by amphetamine, cocaine, methamphetamine, and other addictive stimulants.
It now appears that nicotine is selectively neurotoxic to the other half of the FR tract.
The UCLA researchers exposed rats for 5 days to continuous doses of nicotine, including doses that
produced plasma concentrations of nicotine equivalent to those experienced by humans who smoke a pack
and a half of cigarettes each day. Analysis of the animals' brains revealed highly selective degeneration in
the axons projecting from FR nerve cells. The half of the FR tract damaged by dopaminergic drugs showed
nearly no nicotine-induced degeneration.
- WHAT IT MEANS: The fasciculus retroflexus may represent a "weak link" in the brain for the chronic
drug effects, including addiction and relapse, as a result of use of nicotinic as well as dopaminergic drugs.
The study, led by Dr. Gaylord Ellison, appears in the December 2000 issue of the journal Neuropharmacology.
Brain Hormone That Helps Regulate Food Intake May Dampen Drug Craving: Finding Exploits Possible Relationship Between Addiction and Eating Disorders
Food restriction or deprivation is associated with increased drug use in humans and with increased
self-administration of heroin and cocaine in laboratory animals. Acute food deprivation also potently reinstates
heroin and cocaine seeking in a rat model of relapse to drugs. The neuronal mechanisms underlying this effect,
however, are not known. In experiments using rats, NIDA scientists now report that fasting-induced heroin
seeking is suppressed by leptin, a hormone involved in the regulation of energy balance and food intake.
Rats were trained to self-administer intravenous heroin by pressing a lever. This was followed by a
10-to-13 day period during which lever presses did not yield heroin. When they no longer received heroin,
the rats greatly reduced the number of times they pressed on the lever. Rats were then subjected to one
of several situations, previously shown to induce heroin seekingÐÐ1 day of food deprivation, re-exposure to
heroin, or mild intermittent footshock stressÐÐand then tested to see if they would resume their drug seeking.
Drug seeking in the food-deprived rats was greatly reduced following administration of leptin. Conversely, leptin
did not dampen drug seeking in rats that had received either intermittent footshock stress or heroin injections.
- WHAT IT MEANS: Many people suffering from eating disorders also have drug addiction problems.
This study suggests that medications that target brain systems involved in energy balance and food
consumption may be useful in treating these individuals.
The researchers, Drs. Uri Shalev, Jasmine Yap, and Yavin Shaham of the NIDA Intramural Research Program,
published their findings in the February 15, 2001, issue of The Journal of Neuroscience, Rapid Communications
Section. The paper is posted online at http://www.jneurosci.org.
SPECIAL EVENTS
NIDA Joins in Recognizing National Inhalants and Poisons Awareness Week in March
Nearly one in five students in eighth grade has abused an inhalant sometime during their lifetime, according
to results from the 2000 Monitoring the Future survey, which was funded by NIDA. While this represents
a slight drop from 1999 (19.7 to 17.9 percent), too many children continue to abuse these potentially fatal
substances.
To combat this abuse, NIDA is recognizing National Inhalants and Poisons Awareness Week during the
third week in March by publicizing the availability of science-based informational materials on inhalant abuse.
Inhalants are substances whose vapors can be inhaled to produce a mind-altering effect. Inhalants can
be categorized as follows:
- Volatile solvents, such as paint thinners, degreasers, and glues;
- Aerosols, such as hair sprays and vegetable oil sprays for cooking;
- Gases, including ether, nitrous oxide, and propane; and
- Nitrates, including cyclohexyl nitrate, amyl nitrite, and butyl nitrite.
Inhalants often are among the first drugs that young children use. About 6 percent of children in the United
States have tried inhalants by the time they reach fourth grade. Early recognition of inhalant abuse is important
for parents and physicians. Signs include chemical odors on the breath or clothes, paint or other stains on skin
or clothes, slurred speech, drunk or disoriented appearance, nausea or lack of appetite, and inattentiveness
and lack of coordination.
The most serious hazard for inhalant abusers is a syndrome called "sudden sniffing death." A single,
prolonged session of inhalant use can produce rapid and irregular heart rhythms, heart failure, and death.
"Sudden sniffing death" can happen within minutes and can strike an otherwise healthy young person.
But inhalant abuse can cause death in other ways, too, through asphyxiation, suffocation, or choking.
Chronic exposure to inhalants causes widespread and long-lasting damage to the nervous system and
other vital organs. The toxic chemicals damage parts of the brain that control learning, movement, vision,
and hearing. Damage to the heart, lungs, liver, and kidneys may be permanent.
More information on inhalant abuse can be found on the NIDA Web site at http://www.drugabuse.gov. Free copies
of NIDA's Research Report on Inhalant Abuse and a color poster on inhalants, appropriate for middle-school
children and part of the Institute's award-winning "Mind over Matter" series, may be ordered from the National
Clearinghouse for Alcohol and Drug Information at 1-800-729-6686 or 1-800-487-4889 for the deaf. A fact sheet
entitled "Inhalants" can be ordered from NIDA's Infofax service by calling 1-888-644-6432 or 1-888-889-6432
for the deaf.
UPCOMING EVENTS
- April 4, 2001: Fifth Annual PRISM Awards, 6:30 p.m., CBS Studios, Los Angeles, CA
- April 10, 2001: Prescription Drugs: Misuse, Abuse and Addiction, National Press Club,
Washington, DC.
- July 19-20, 2001: Advances in MDMA (Ecstasy) Research, William H. Natcher Conference Center,
NIH Campus, Bethesda, MD
- August 9-10, 2001: 2nd National Conference on Drug Abuse Prevention Research: A Progress Update,
Omni Shoreham Hotel, Washington, DC.
- September 24-26 2001: National Conference on Health Disparities Among Racial and Ethnic Groups,
Wyndham Franklin Plaza Hotel, Philadelphia, PA
Watch upcoming issues of NewsScan for more information on these events, or call NIDA at 301-443-6245.
For more information about any item in this NewsScan:
- Reporters, call Michelle Muth at 301-443-6245.
- Congressional staffers, call Mary Mayhew at 301-443-6071.
The National Institute on Drug Abuse is a component of the National Institutes of Health, U.S. Department of
Health and Human Services. NIDA supports more than 85 percent of the world's research on the health aspects
of drug abuse and addiction. The Institute carries out a large variety of programs to ensure the rapid dissemination
of research information and its implementation in policy and practice. Fact sheets on the health effects of drugs
of abuse and other topics can be ordered free of charge in English and Spanish by calling NIDA Infofax at
1-888-NIH-NIDA (644-6432) or 1-888-TTY-NIDA (889-6432) for the deaf. These fact sheets and further information
on NIDA research and other activities can be found on the NIDA home page at http://www.drugabuse.gov.
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