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Testosterone May Be Addictive

MIAMI BEACH, FLORIDA--Some athletes and bodybuilders pump themselves with anabolic steroids, compounds that mimic or stimulate the hormone testosterone, to bulk up fast. New research presented yesterday at the Society for Neuroscience's annual meeting suggests that testosterone itself is addictive for rats. If people too get hooked on the hormone, that could help explain the growing phenomenon of steroid abuse.

The Olympic committee banned steroids in 1975, and most professional sports have done likewise. In 1991, the Drug Enforcement Agency declared testosterone a controlled substance, putting it in the same category as heroin and cocaine. Steroid users who go off the stuff do experience withdrawal symptoms such as depression and anxiety, but there was no direct evidence of addiction.

Insights into the physiology of addiction often come from rats, which develop cravings for some of the same drugs as humans. Given a chance to control how much heroin, cocaine, or amphetamine gets pumped into their veins, rats will do whatever's necessary to get their fix.

A team of Yale researchers led by obstetrician-gynecologist Luke Johnson, now at New York University, used two techniques to test whether rats will also voluntarily give themselves doses of testosterone. In one experiment, they allowed the rats to drink Kool-Aid that was either straight or spiked with testosterone. In another approach, rats could get a shot of testosterone if they poked their noses in a given hole. In both cases, rats voluntarily and repeatedly dosed themselves with the hormone.

"It's an important step to show that rats will self-administer testosterone," says psychologist Mark Packard of Yale University. His research suggests that testosterone acts in the brain on the same neurotransmitter system--the mesolimbic dopamine pathway--that other addictive drugs stimulate. "The field is at an early stage," he says, but so far the evidence supports the idea that anabolic steroids are addictive, an understanding that could help guide treatment strategies for steroid users trying to kick the habit.