Brain Scans Prove Dopamine's Involvement In Cocaine Abuse

November 14, 1997

Scientists at Johns Hopkins have used brain scans to show that intravenous doses of cocaine increase the availability of dopamine, the brain's "feel-good" chemical.

Dopamine's activity appeared to increase two to three times over baseline levels in the brain area studied, the putamen, compared to a control area, the cerebellum.

Although the increase cannot yet be directly linked to a cocaine user's "high," investigators report that this is the first time anyone has directly demonstrated that cocaine makes more dopamine available in the human brain.

Improvements in scanning technology eventually may track cocaine's effects on the dopamine-generating nucleus accumbens, a smaller area nearby in the brain that is known to play a role in addictive behavior in animals, adds Godfrey Pearlson, M.D., professor of psychiatry and a lead author on the paper.

"The new finding should advance efforts to understand addiction and treat it by blocking the euphoric effects of drugs," says Pearlson.

Brain cells use dopamine by binding the chemical to specific openings on their surfaces. Pearlson used these openings to measure dopamine activity. First, he injected cocaine users with the compound raclopride, which binds to these same receptors. The raclopride was equipped with a mildly radioactive "tag" visible on positron emission tomography (PET) brain scans.

Soon after, scientists gave the subjects an injection of a placebo and scanned their brains. Several hours later, the same subjects received a second dose of raclopride followed by a "street-equivalent" dose of cocaine. Then they scanned the patients again.

"Because the raclopride and dopamine compete for the right to bind to the same receptors, we could compare the two sets of scans and be virtually certain that the differences in the second group were caused by extra dopamine produced by cocaine exposure," says Thomas Schlaepfer, M.D., now at the University of Bern in Switzerland.

"It's likely cocaine affects other neurotransmitters besides dopamine, and these may also be helping create the immediate rush' or feeling of euphoria caused by cocaine," Pearlson explains. "But dopamine is still obviously a very important part of drug addiction. Marijuana, alcohol and heroin all initially act on different brain systems, but the common bond between them is that they all also increase dopamine availability."

The study, published with an accompanying commentary, in the September issue of the American Journal of Psychiatry, was funded by the National Institutes of Health, the Swiss National Science Foundation, the Roche Research Foundation, the CIBA Research Foundation, and other government and private sources. Other authors were Dean Wong, M.D.; Stefano Marenco, M.D.; and Robert Dannals, Ph.D.

--JHMI--

Media contact: Michael Purdy (410)955-8725
E-mail: mpurdy@welchlink.welch.jhu.edu


Johns Hopkins Medical Institutions' news releases are available on a PRE-EMBARGOED basis on EurekAlert at http://www.eurekalert.org, Newswise at http://www.newswise.com and from the Office of Communications and Public Affairs' direct e-mail news release service. To enroll, call 410-955-4288 or send e-mail to bsimpkin@welchlink.welch.jhu.edu or 76520.560@compuserve.com.

On a POST-EMBARGOED basis find them at http://hopkins.med.jhu.edu, Quadnet at http://www.quad-net.com, ScienceDaily at http://www.sciencedaily.com or on CompuServe in the SciNews-MedNews library of the Journalism Forum under file extension ".JHM".

Johns Hopkins Medicine

Related Cocaine Articles from Brightsurf:

Sleep-deprived mice find cocaine more rewarding
Sleep deprivation may pave the way to cocaine addiction. Too-little sleep can increase the rewarding properties of cocaine, according to new research in mice published in eNeuro.

Nucleus accumbens recruited by cocaine, sugar are different
In a study using genetically modified mice, a University of Wyoming faculty member found that the nucleus accumbens recruited by cocaine use are largely distinct from nucleus accumbens recruited by sucrose, or table sugar.

Astrocytes build synapses after cocaine use in mice
Drugs of abuse, like cocaine, are so addictive due in part to their cellular interaction, creating strong cellular memories in the brain that promote compulsive behaviors.

Of all professions, construction workers most likely to use opioids and cocaine
Construction workers are more likely to use drugs than workers in other professions, finds a study by the Center for Drug Use and HIV/HCV Research (CDUHR) at NYU College of Global Public Health.

Chronic cocaine use modifies gene expression
Chronic cocaine use changes gene expression in the hippocampus, according to research in mice recently published in JNeurosci.

Blocking dopamine weakens effects of cocaine
Blocking dopamine receptors in different regions of the amygdala reduces drug seeking and taking behavior with varying longevity, according to research in rats published in eNeuro.

Born to run: just not on cocaine
A study finds a surprising response to cocaine in a novel strain of mutant mice -- they failed to show hyperactivity seen in normal mice when given cocaine and didn't run around.

Cocaine adulterant may cause brain damage
People who regularly take cocaine cut with the animal anti-worming agent levamisole demonstrate impaired cognitive performance and a thinned prefrontal cortex.

Setting affects pleasure of heroin and cocaine
Drug users show substance-specific differences in the rewarding effects of heroin versus cocaine depending on where they use the drugs, according to a study published in JNeurosci.

One in 10 people have traces of cocaine or heroin on their fingerprints
Scientists have found that drugs are now so prevalent that 13 percent of those taking part in a test were found to have traces of class A drugs on their fingerprints -- despite never using them.

Read More: Cocaine News and Cocaine Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.