Neurobehavioral consequences of adolescent nicotine exposure
Abstracts
Initial Award Abstract |
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Recent research surveys have uncovered that over 20% of all adolescents, between the ages of 12 and 18, are smokers. In young adults who decide to smoke, smoking onset appears to peak between the ages of 14-16 years. Unfortunately, beginning smoking during young adulthood has been shown to produce several serious outcomes. Adolescent smokers are more likely to become heavy smokers, they are much less likely to quit smoking later in their life, and are more likely to die from smoking-related illnesses. This suggests the initiation of smoking during adolescence will continue to have dramatic long-term consequences on world-wide health care costs. It has been suggested that these findings of poorer outcome for early onset smokers may due to the fact that young adults may be at higher risk for developing a stronger physical dependence on smoking. Thus it appears that smoking is “more addictive” when a person begins smoking during adolescence. The reason for this higher risk for addiction to smoking during adolescence is not entirely understood. However, it is likely due to the fact that the brain goes through rapid and dramatic physical changes during that time. As many as 50% of the connections in many brain regions are eliminated during adolescence. This developmental process called brain "pruning" allows the brain to assume its adult form. It appears that this brain process while critical for adult development also puts the brain “at risk” for drug abuse and perhaps also the toxic effects of drugs. It seems that changes that occur in the adolescent brain may resemble in some ways another critical time in development, the “brain growth spurt” that occurs during late fetal development. We have demonstrated, in animal studies, that nicotine exposure during the brain growth spurt has long term consequences for brain development. However, there have been no systematic studies assessing the long-term effects of nicotine on brain and behavior in animals exposed during the adolescent “pruning” period. Therefore, animal models of nicotine exposure have the potential to allow us to greatly enhance our understanding of nicotine's effects during adolescence. Brain measures such as electroencephalography (brain waves, EEG) and event-related potentials (ERPs) are very sensitive to changes in central nervous system function which occur as a result of nicotine exposure. These brain measures as well as assessment of critical behaviors will allow us to more fully assess the effects of adolescent nicotine exposure. We predict that chronic nicotine exposure alters brain mechanisms involved in the regulation of stress and anxiety. Given that smoking has been related to stress levels, these alterations in response to stress are bound to alter future smoking patterns. Thus the proposed experiments will examine long term changes in brain function and behavior following adolescent nicotine exposure. This will lay the foundation for identifying what brain systems are particularly affected by adolescent nicotine exposure. In addition, if the underlying causes for the high rate of smoking initiation among adolescents can be identified then their increased risk for progression to higher smoking levels, and their decreased chances of successfully quitting smoking may also be explained. |
Final Report |
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Recent health surveys have revealed that over 20% of all adolescents, between the ages of 12 and 18, are smokers. In young adults who decide to smoke, smoking onset appears to peak between the ages of 14-16 years. Unfortunately, beginning smoking during young adulthood has been shown to produce several serious outcomes. Adolescent smokers are more likely to become heavy smokers, they are much less likely to quit smoking later in their life, and are more likely to die from smoking-related illnesses. This suggests the initiation of smoking during adolescence will continue to have dramatic long-term consequences on world-wide health care costs. It has been suggested that these findings of poorer outcome for early onset smokers may due to the fact that young adults may be at higher risk for developing a stronger physical dependence on smoking. Thus it appears that smoking is "more addictive" when a person begins smoking during adolescence. The reason for this higher risk for addiction to smoking during adolescence is not entirely understood. However, it is likely due to the fact that the brain goes through rapid and dramatic physical changes during that time. This developmental process allows the brain to assume its adult form. It appears that this brain process while critical for adult development also puts the brain "at risk" for drug abuse and perhaps also the toxic effects of drugs. It seems that changes that occur in the adolescent brain may resemble in some ways another critical time in development that occurs during late fetal development. We have demonstrated, in animal studies, that nicotine exposure during early life has long term consequences for brain development. However, there have been fewer systematic studies assessing the long-term effects of nicotine on brain and behavior in animals exposed during adolescence. In many ways the development of the rat brain is similar to the development of the human brain with both rat and human brains having similar critical periods of development. Therefore, animal models of nicotine exposure have the potential to allow us to greatly enhance our understanding of nicotine's effects during adolescence. Our studies propose to develop the use of transdermal nicotine patches to expose adolescent rats to relevant doses of nicotine. Brain measures such as electroencephalography (brain waves, EEG) and event-related potentials (ERPs) are very sensitive to changes in central nervous system function which occur as a result of nicotine exposure. These brain measures as well as assessment of critical behaviors will allow us to more fully assess the effects of adolescent nicotine exposure. We predict that chronic nicotine exposure during adolescence alters brain mechanisms involved in the regulation of stress and anxiety. Given that smoking has been related to stress levels, these alterations in response to stress are bound to alter future smoking patterns. Thus the proposed experiments will examine long term changes in brain function and behavior following adolescent nicotine exposure. This will lay the foundation for identifying what brain systems are particularly affected by adolescent nicotine exposure. |
