The voluntary consumption of drugs is a behavior found in a number of species of animal. But until now it was thought that drug-addiction was a specific behavior of humans.
New research released by INSERM, the French Institute of Health and Medical Research today, shows that the behaviors which define drug-addiction in humans, can also appear in the rat when cocaine is consumed.
Drug-addiction in humans and rodents presents astonishing similarities. The discovery of drug dependence in the rat strongly suggests that drug-addiction is a true disease of the brain. These new findings should make it possible to better understand the biology of drug-addiction and improve treatments. The study is published in the current issue of Science Review.
The principal objective of any researcher who studies drug dependency is to understand the mechanisms that lead to addiction. Addiction is not classed as simply drug-taking but prolonged compulsive consumption in spite of the consequences. Compulsive consumption of drugs or addiction generally only occurs in 15-20% of the overall human drug using population and has the characteristics of a chronic disease, since the rate of relapse, even after prolonged periods of abstinence, is always very high (approximately 90%).
Until now, no true model existed for drug addiction in animals, limiting the understanding of drug dependence.
This is why the Inserm team wanted to test if drug addiction could be observed in rodents. The researchers studied the voluntary consumption of cocaine in 100 rats. The rats, free to move, consumed cocaine by inserting their muzzles into a hole in one of the walls of their "experimental room".
The animals were studied in this environment for three months. This period is a substantial portion of a rats life as average life expectancy is only two years.
Three behaviors were specifically watched for. These behaviors are considered to be standard diagnostic tests for drug dependency in humans.