American scientists have found that excessive enthusiasm for sports exercises can cause physical dependence, similar to the heroin. In an experiment in rats, the introduction of a drug that causes a withdrawal syndrome in opioid addicts, to animals after a long run in the wheel, led to the development of a similar syndrome, according to PhysOrg.
The greatest similarity with drug addiction was found in "athletic anorexia" - a condition in which excessive exercises (usually started with the goal of weight loss) become an irresistible need that is combined with a sharply reduced appetite, leading to severe, often lethal exhaustion.
Researchers from Tufts University in Massachusetts placed 44 males and 40 female laboratory rats in conditions where they could choose to run in the wheel or neglect physical activity. After several weeks, the animals were divided into two groups: "active", intensely engaged in running, and "inactive", preferring to rest.
To simulate "athletic anorexia," each group of animals was divided into two parts: one was given access to food for one hour a day, the other could eat unlimitedly.
After a while, animals from all four groups were injected with naltrexone, an opioid receptor antagonist, which causes "breakage" in addicts who are addicted to heroin, morphine and the like.
In response to the administration of the drug, "active" rats developed a typical withdrawal syndrome: they trembled, wriggled, and gnashed their teeth. The most pronounced symptoms were observed in animals running more than others with reduced food intake.
The reaction of "inactive" rats to the administration of naltrexone, regardless of the diet, was insignificant.
According to Robin Kanarek, the head of the study, excessive exercises lead to increased production of "mediators of pleasure" in the brain - endorphins and dopamine, which corresponds to biochemical changes in the use of opiate drugs.
Scientists hope that the results they obtained can be applied "in the opposite direction" - to develop methods for rehabilitation of drug addicts with exercise.
Medicinform. Net.