Nicotine Reaches The Brain Slowly

By Margarita Nahapetyan

Nicotine takes much longer than it was previously thought to build up and reach peak levels in the brain of a smoking person, claims a new research by experts at Duke University Medical Center, U.S.

Scientists tended to believe that nicotine inhaled in a puff of cigarette smoke took just 7 seconds to be taken up and absorbed by the brain, and that each puff was producing a spike of nicotine. In other words, two of the most popular hypotheses to explain the development and maintenance of strong nicotine dependence in smoking people were fast accumulation of nicotine by the brain during cigarette smoking and puff-associated spikes in brain nicotine concentration.

But in their new study, for the first time, Duke researchers showed that smokers of cigarettes actually experience a steady rise of nicotine levels in the brain during the process of smoking a whole cigarette. According to Jed Rose, PhD, director of the Duke Center for Nicotine and Smoking Cessation Research, it was thought before that the puff-by-puff spikes of nicotine that were going straight to the brain explained why cigarettes are so much more addictive when compared to other forms of nicotine delivery, such as the patch or gum, for example. The current study, however, raises the question whether addiction is associated 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," Dr. Rose said.

To come up with this conclusion, Dr. Rose and his fellow colleagues analyzed the dynamics of nicotine accumulation in the brain of a smoking person during actual cigarette smoking using PET scanning. The experts had 11C-nicotine loaded into cigarettes of 13 regular smokers and 10 individuals who smoked only from time to time, an indication that they were not addicted to nicotine.

The results revealed that maximum brain levels of nicotine were reached in between three and five minutes, and built up slower in regular smokers when compared to occasional ones. The experts suggested that this slower rate was a result of nicotine staying longer in the lungs of addictive smokers, which could be a result of the chronic effects of smoke on the lungs. Now that the scientists revealed that there are not these spikes that had been expected, Rose said, they may be better able to develop new ways in order to help smokers get what they need from cigarettes, but in a way that is not or less addictive.

The findings were published in the Early Edition of the Proceedings of the National Academy of Sciences journal on March 8.