Nicotine takes much longer than previously thought to reach peak levels in the brains of cigarette smokers, says a new study by Duke University Medical Center researchers.
Scientists previously thought that nicotine inhaled in a puff of cigarette smoke took a mere seven seconds to be taken up by the brain, and that each puff produced a spike of nicotine.
Using PET imaging, Duke researchers demonstrated, for the first time, that cigarette smokers actually experience a steady rise of brain nicotine levels during the course of smoking a whole cigarette.
According to the researchers, the findings could lead to more effective treatments for smoking addiction.
"Previously it was thought that the puff-by-puff spikes of nicotine reaching the brain explained why cigarettes are so much more addictive than other forms of nicotine delivery, like the patch or gum," says Jed Rose, director of the Duke Center for Nicotine and Smoking Cessation Research.
"Our work now calls into question whether addiction has to do with the puff-by-puff delivery of nicotine. It may actually depend in part on the overall rate at which nicotine reaches and accumulates in the brain, as well as the unique habit and sensory cues associated with smoking," Rose added.
Yet, when the researchers compared 13 dependent smokers to 10 non-dependent smokers, they were surprised to find the dependent smokers had a slower rate of nicotine accumulation in the brain.
"This slower rate resulted from nicotine staying longer in the lungs of dependent smokers, which may be a result of the chronic effects of smoke on the lungs," said Rose.
The study has been published online in the Early Edition of Proceedings of the National Academy of Sciences (PNAS) the week of March 8.