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Heroin May Impair Stress Response

Rat studies point to 'vicious cycle' that could spur abuse

WEDNESDAY, Aug. 31 (HealthDay News) -- Animal studies suggest that the use of opiate drugs, which include morphine and heroin, can leave users more vulnerable to stress, creating a vicious cycle of use and abuse.

Not only does stress trigger the drug use, but in return the drug leaves animals more vulerable to that stress, researchers at the University of New South Wales report in the current issue of Behavioral Neuroscience.

In the study, scientists injected rats with either morphine or a saline solution for 10 days. They then performed a stress test on them by gently restraining each rat for 30 minutes.

In the absence of stress, opiate-treated rats behaved the same as the other rats. But when subjected to stress, they appeared to suffer twice as much as non-drugged rodents.

The longer the duration or the higher the dose of morphine, the greater the difference in this stress reaction, the researchers found.

The research could explain why people who use opiates such as heroin have very high rates of anxiety problems, including post-traumatic stress disorder, even after they stop using, researchers said. That emotional fragility also can also make them more likely to start using again, the Australian team said.

More information

The National Institute on Drug Abuse has more about heroin addiction.

-- Dennis Thompson

SOURCES: American Psychological Association, news release, Aug. 28, 2005

Last Updated: Aug-31-2005