There�s more evidence the key to human behaviors such as addiction and aggression may lie in your genes. In one study, University of Colorado behavioral scientists found that mice with an alteration in a gene called Chrna4 consumed much more nicotine than mice with another form of the same gene.
The researchers believe that this addiction-linked change in the gene, called a "threonine polymorphism," may enable mice to tolerate higher levels of nicotine before they suffer nervous system side effects.
In a prepared statement, co-researcher Jerry Stitzel stressed that "no single gene is going to be the sole determinant of whether someone will become addicted to nicotine or any other substance, because addiction likely is due to the effects of many genes, as well as social and other environmental factors."
However, with each new gene that�s uncovered, "we will gain important knowledge about the biology of addiction," he said. "With that, we will be in a much better position to design more effective treatments for addiction," including anti-smoking therapies.
The Chrna4 gene is found in virtually all animals, including humans, the researchers explained, and is a key player in regulating the brain chemical acetylocholine. Acetylcholine plays a role in the brain�s pleasure system and in learning, memory, sleep, heart rate, blood pressure, muscle movement and other functions.
Nicotine is chemically similar to acetylcholine, and the Colorado team believes this might help explain why specific variations of the Chrna4 gene have such a powerful impact on nicotine addiction.
In a second study, German researchers found specific components of aggressive behavior seemed to be linked to the "U" variation of the TPH gene -- a marker that may be connected to another, as yet unidentified, gene.
According to the researchers, their findings contribute to growing evidence that aggressive behavior -- often labeled as psychopathic or sociopathic -- may have a genetic basis involving abnormally low levels of the neurotransmitter serotonin.
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