http://www.scripps.edu/news/press/2013/2...taffe.html a écrit :

In a standard method for evaluating stimulant drugs, the animals were able to dose themselves intravenously by pressing a lever. As is typical for addictive stimulants, the rats maintained a steady self-administration of each drug whenever they could. In one set of tests designed to quantify how much the rats desired each drug, they could get another infusion only by making ever-greater numbers of lever presses.

“When we increased how many lever presses a rat would have to emit to get an additional infusion of drug, we observed that rats emitted about 60 presses on average for a dose of METH but up to about 600 for MDPV—some rats would even emit 3,000 lever presses for a single hit of MDPV,” said TSRI Research Associate Shawn M. Aarde, who was first author of the study. “If you consider these lever presses a measure of how much a rat will work to get a drug infusion, then these rats worked more than 10 times harder to get MDPV."