Genetic factors play an important role in the continuing addiction to cigarettes, suggest scientists at Washington University School of Medicine in St. Louis.//
Results of two studies show that certain genetic variations can influence smoking behaviors and contribute to a person's risk for nicotine dependence.
Scientists suggest that these smoking-related genes may facilitate communication between nerve cells in the brain. One gene in particular, the alpha-5 nicotinic cholinergic receptor (CHRNA5) gene, was a very strong indicator of risk for nicotine dependence.
Individuals with a specific variation in the gene show a two-fold risk of developing nicotine dependence once exposed to cigarette smoking.
CHRNA5 is from a class of receptors that plays a role in dopamine pathways in the brain, which are linked to a person's experience of pleasure.
The researchers also identified genes related to gamma aminobutyric acid (GABA) receptors, another set of proteins vital to nerve cell function. Both GABA and nicotinic receptors had been suspected of involvement in nicotine addiction, but these findings strengthen those suspicions.
The studies also identified a gene not previously known to be involved with nicotine dependence. Called the Neurexin 1 (NRXN1) gene, it helps regulate the balance between excitatory mechanisms — those that increase communication between nerve cells — and inhibitory mechanisms — those that slow firing between nerve cells.
"An imbalance between excitatory and inhibitory activity in the brain may predispose people to addiction, such as alcoholism, drug dependence or nicotine dependence," says Laura Jean Bierut, M.D., associate professor of psychiatry and principal investigator of both studies. "The Neurexin gene we've identified is really a key factor in the balance between inhibition and excitatory activity in neurons."
Bierut suspects a large number of genes are involvedPage: 1 2 3 4 Related medicine news :1
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