Yale researchers and other scientists have discovered that the adolescent brain launches a strong defensive reaction when first exposed to cocaine. Two new studies identify the genes responsible for this reaction; the hope is to determine why the risk of drug addiction drastically increases if a person starts using as a teenager. In the first study, researchers found that teens have a much higher vulnerability to cocaine than adults mainly because the adolescent brain is shifting from an explosive, plastic growth phase to more settled and refined neural connections. Past studies at Yale have shown that this change in the brain’s shape is regulate by the gene "intergrin beta 1," which plays an essential role in the development of the nervous system."This suggests that these structural changes observed are probably protective of the neurocircuitry, an effort of the neuron to protect itself when first exposed to cocaine," says Anthony Koleske, senior author of both papers. In the second study, Yale researchers found that when cocaine-using mice had their integrin beta 1 pathway knocked out, they needed three times less coke to bring about behavioral changes. "If you were to become totally desensitized to cocaine, there is no reason to seek the drug," says Koleske. The results suggest that the intergrin beta 1 pathway plays a huge role in why some teen cocaine users become addicted and others don't.