Impulsivity and Addiction
People addicted to drugs are usually high in novelty seeking and in impulsivity, but it is not clear whether these traits result from the drug's assault on the brain; and if they are causal agents of addiction, it is uncertain how much each trait contributes. Researchers at Cambridge University in England suspected that addiction depends primarily on impulsivity. Testing their hypothesis with humans would require procedures that would be considered unethical but, fortunately, rats also demonstrate these behavioral traits. Novelty seeking appears as an atypically high level of exploration in a new environment, while impulsivity is seen in behaviors like pressing a lever before the rat is signaled to do so. When rats classified as high in novelty seeking were allowed to self administer cocaine into their brains, they did so readily and administered high doses. But after 40 days they had lost interest in the cocaine. Rats high in impulsivity were slower to adopt self administration and administered less of the drug; but over time they appeared addicted, unable to refrain from the drug even when it meant getting an electric shock. Thus novelty seeking may lead to drug experimentation, but impulsivity appears more critical for the development of addiction. Science, Vol 320, 1352-1355.
A Possible New Treatment for Alcoholism
Naltrexone, which blocks opioid receptors, is widely used in alcoholic rehabilitation; however, it works better with early-onset alcoholics than with late-onset alcoholics, who drink primarily to relieve stress. Help may be on the way in the form of a drug that blocks the neurokinin 1 receptor, a receptor for substance P that mediates stress behavior. The drug reduced craving in recovering alcoholics who were high in anxiety, compared to similar controls receiving a placebo. Following an emotional stress test, they reported less stress and blood tests indicated less cortisol increase. Functional MRI scans showed that the drug-treated group also responded less in the brain's emotion areas to pictures designed to elicit negative emotions. Science, Vol 319, 1536-1539.
