WINSTON-SALEM, N.C. – New research in monkeys suggests that, although living in an "enriched" environment can make someone less vulnerable to abusing cocaine, once started, extended drug abuse can eliminate the social advantage the abuser originally had.
However, the research also shows that prolonged abstinence from drug use can give the recovering addict another chance, and that environment again becomes a major factor influencing the success of the recovery.
Michael A. Nader, Ph.D., professor of physiology/pharmacology and of radiology at Wake Forest University Baptist Medical Center, delivered those findings today in a course for medical professionals presented by the American Society of Addiction Medicine (ASAM).
Nader said the animal research has important implications for physicians and other practitioners working with human addicts. "The most important thing that we have shown is that environmental enrichment can protect the individual from the likelihood that they'll abuse cocaine.
"There have been many studies that show that stress – the other end of that continuum – can increase the likelihood that an individual will abuse drugs. We've gone to the other side of that and shown that enrichment can actually protect the individual from drug abuse."
The ASAM course, "Addiction Across the Lifespan," was scheduled to include presentations by Paul Greengard, Ph.D., a Nobel laureate, and Nora Volkow, M.D., director of the National Institute on Drug Abuse.
Nader, one of only three animal researchers included on the program, told the group that research has focused both on behavioral patterns and on actual physiological changes in brain chemistry in animal models. He said that the animal research can verify hypotheses that can't be tested in human subjects, due to ethical considerations.
The physiological aspects have dealt with the chemistry of dopamine, a major neurotransmitter in the brain. Cocaine increases levels of dopamine, which is apparently the cause of the intense but fleeting euphoria experienced by cocaine users. Increased levels of dopamine over long-term cocaine use causes the brain to adjust by reducing the number of dopamine (D2) "receptors."
Nader said that research has shown that social "rank" in animal populations has a significant effect on whether a monkey will take cocaine. That effect has a direct correlation with the level of D2 receptors a monkey has, as measured by noninvasive brain imaging: Dominant monkeys have more D2 receptors and are less likely to abuse cocaine than the subordinate monkeys.
But, he said, the monkeys don't start out that way. It is the social environment itself that creates the difference in brain chemistry over time. Monkeys that become dominant have an enriched environment – more freedom, less fear, more grooming by other monkeys – while the subordinates live with more stress.
New research, Nader said, has shown that after the dominant monkeys start abusing cocaine, their D2 receptors decrease over time. Once they are taken off cocaine, however, the D2 receptors increase again with six to nine months' abstinence. And, given the opportunity to use cocaine again, he hypothesizes that they will be less likely to relapse, compared with the subordinate monkeys.
Nader and colleague Paul W. Czoty, Ph.D., assistant professor of physiology and pharmacology, described the recent research in a paper published in August in the American Journal of Psychiatry.
Nader said that human examples of environmental enrichment include a job, educational opportunity, and strong family support.
And he said that practitioners and family members must understand the importance of abstinence. In humans, he said, it could take years for the brain to recover, but he believes it can eventually. "You have to remove them from the environment that they're in where the drugs are being taken, because the environment has huge effects on the dopamine system and on the likelihood that they'll take drugs," Nader said.
When they are abstinent, they can return to normal. "Some people have a view that once you're addicted, you're always addicted, and I think part of that is because of the environment.
"These data could argue that the brain does bounce back. It's not a permanent change," Nader said. "They're not damned because they've been taking cocaine. Things can return. I think that's a promising message – that, and the fact that the environment can, in fact, protect the individual." Current research, he said, is testing whether non-addictive drugs that increase the D2 receptors in the brain could have the same effect as an enriched environment, and therefore protect a recovering addict against relapse.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
Published on PsychCentral.com. All rights reserved.
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