Teens are known to be more likely to smoke if their mothers smoked during pregnancy. Among the possible explanations for this phenomena could be a genetic predisposition that increased the odds of mothers being smokers in the first place. However, epidemiological studies which have controlled for many factors support the idea of a biological cause that is a result of the prenatal exposure. Dr. Theodore Slotkin of Duke University has produced evidence in a rat model that suggests prenatal nicotine exposure causes brain damage that creates a predisposition to nicotine addiction.
The rats exposed to nicotine before birth suffered loss of brain cells and a decline in brain activity that persisted throughout adolescence and into adulthood, the team found.
When given doses of nicotine for a two-week period as adolescents, the earlier exposed rats showed a weaker brain response in circuits using acetylcholine -- a natural chemical messenger that plays a critical role in learning and memory -- as compared to rats that did not experience the prenatal exposure. Nicotine's activity in the brain stems from its ability to mimic acetylcholine. The earlier exposure also worsened the decline in brain activity during nicotine withdrawal and led to an increase in the amount of brain cell injury induced by the drug, they reported.
"The current study suggests that the lasting neurotoxic effects of prenatal exposure to nicotine from maternal smoking during pregnancy may worsen the long-term consequences of adolescent smoking -- effects that may increase the likelihood that an individual will take up and keep smoking," Slotkin said.
Specifically, the team explained, the reduced response of acetylcholine systems in the adolescent brain following prenatal exposure might lead teens to self-administer nicotine in an attempt to replace the brain's functional loss. Furthermore, that deficient brain response might drive higher cigarette consumption.
Here is the abstract of the paper and that includes a link to the full paper.
Another group of Duke researchers has previously shown in a rat model that initial exposure to nicotine more strongly predisposed the rats toward later nicotine cravings if the initial exposure first happened in adolescence rather than in adulthood. Brains that are still developing are generally more vulnerable to toxins and so this result is not too surprising.
It is also worth noting that hostile personalities are more prone to nicotine addiction. This latest result suggests the possibility that prenatal nicotine exposure might make people more hostile later in life.
|Share |||Randall Parker, 2004 April 20 11:57 AM Brain Addiction|