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Popular “Bath Salt” Hooks Lab Rats

Posted Jan 18 2013 5:23pm

Mephedrone shows addictive properties in animal models.

Cathinones, like methedrine and other stimulants, are primarily dopamine-active drugs. Though they are now illegal in the U.S., they were formerly of primary interest only to pharmaceutical researchers. The best-known cathinone sold in the form of bath salts and plant food—mephedrone—has both dopamine and serotonin effects. It broke big in the UK a few years ago as a “legal” party drug alternative to MDMA. The idea was to get high without testing dirty, as the saying goes.

Behavioral clues about mephedrone have been teased out of rat studies. The Taffe Laboratory at Scripps Research Institute has been focusing on the cognitive, thermoregulatory, and potentially addictive effects of the cathinones, and mephedrone in particular. Scripps researchers have carried the investigation forward with a recent study in the journal Drug and Alcohol Dependence.

Now comes additional evidence, also from the Taffe Lab at Scripps, that mephedrone, or 4-MMC, looks like an addictive drug. In a paper accepted for publication by Addiction Biology, which Addiction Inbox was allowed to review in advance, Dr. Michael Taffe, along with lead author S.M. Aarde and coworkers, demonstrated in an animal study that lab rats will intravenously self-administer mephedrone under normal lab conditions—roughly analogous to shooting speed.

Without suitable strains of test animals, most genetic and neurobiological research would take centuries, and would involve ethical questions about human testing far stickier than the questions raised by work with animals. Animal models are one of the primary pathways of discovery available to neurobiologists and other researchers.

But it’s tricky. Establishing traditional rodent laboratory conditions is a Goldilocks endeavor: The environment must be not too hot, but not too cold, because this can effect rodent behavior. And the drug must be given at rates that are not too frequent and not too rare.

The curious thing about mephedrone is that it appears to combine the effects of prototypical stimulants like cocaine and methamphetamine, with the trippy, “entactogen” effects of MDMA, aka Ecstasy, in the bargain. The drug rapidly crosses the blood-brain barrier, reaching peak levels two minutes after injection, and full effects last about an hour. In one study, 76% of people who had snorted both cocaine and mephedrone reported that the quality of the mephedrone high was “similar to or better than” cocaine. But the paper also states that “human recreational users report 4-MMC to be subjectively similar to MDMA.”

The investigators ran a series of tests with various groups of rats, and found that 80-100% of the rats would happily reward-press a lever for an infusion of mephedrone. “Under these conditions,” writes Taffe, “methamphetamine and 4-MMC have about equal effect on rat self-administration although the 4-MMC is considerably less potent, requiring about 10 times the per-infusion dose for effect.” Although it wasn’t demonstrated directly in this paper, Ecstasy “is at best unevenly self-administered by rats,” and “despite an MDMA-like serotonin/dopamine neuropharmacological effect, mephedrone has a liability for repetitive intake more similar to the classical amphetamine-type stimulants such as methamphetamine.”

It’s a weaker type of stimulant, mephedrone, but it does the trick. It is highly reinforcing. Mephedrone chemically resembles speed, but also has Ecstasy-like effects. "Furthermore, neurochemical data suggest MDMA-like patterns of relatively greater serotonin versus dopamine accumulation in nucleus accumbens.” Even with its added Ecstasy-like effects, the scientists conclude that “the potential for compulsive use of mephedrone in humans is likely quite high, particularly in comparison with MDMA.”

Photo Credit: Creative Commons
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