European scientists find that rats can become addicted to cocaine
Two studies by French and UK scientists have found that rats that take cocaine on a regular basis behave in the same way as human addicts. These new findings, published in the journal Science, will offer a way to help researchers understand what makes some people particularly vulnerable to addiction, and will enable them to test anti-drug therapies. The French team, from the National Institute for Research and Health (INSERM), trained rats to poke their noses through holes in their cages to trigger injections of cocaine. After letting them develop a habit over three months, the scientists then put them through three experiments to test whether they had trouble stopping, how motivated they were to get another 'hit', and whether an electric shock would deter them from continuing. 'Preliminary results show similar changes in brain activity between rats showing addiction-like behaviours and human addicts,' wrote the researchers. Although all of the rats enjoyed taking cocaine, only 17 percent of them developed a drug addiction, compared to 15 per cent of humans who regularly use cocaine, found the French team The UK study, lead by Louk Vanderschuren and Barry Everitt from the University of Cambridge, showed that rats that had been accessing cocaine for extended periods of time continued to do so even when their feet were shocked. However, rats that had used cocaine for a short period quit after they knew of the punishment. Compulsive drug-seeking even in the face of negative consequences is a measure of human addiction, say the researchers. Both studies concluded that extended exposure to cocaine is a key to addiction. Pier Vincenzo Piazza from the INSERM team, however, insisted that the exposure must be combined with some underlying genetic vulnerability, which would explain why not all rats became addicted. Both studies also found that relapses by former addicts are very common. Tests on addicted rats showed that 90 per cent of them returned to compulsive cocaine use even after long periods of going without. This is the same with humans. Thus, stated both studies, drug rehabilitation techniques concentrating on vulnerable individuals will have to take into account long-term use as well.
Countries
France, United Kingdom