Researchers at the University of California at Los Angeles have found that so-called "light" cigarettes deliver nearly as much nicotine to the brain as regular cigarettes.

The authors studied positron emission tomography (PET) scans of 15 smokers participating in the study and found that smoking de-nicotinized cigarettes and low-nicotine cigarettes led to 26 percent and 79 percent occupancy, respectively, of the brain's receptors. Regular cigarettes have been found to occupy 88 percent of nicotine receptors.

"The two take-home messages are that very little nicotine is needed to occupy a substantial portion of brain nicotine receptors, and cigarettes with less nicotine than regular cigarettes, such as 'light' cigarettes, still occupy most brain nicotine receptors," researcher Arthur Brody said. "Thus, low-nicotine cigarettes function almost the same as regular cigarettes in terms of brain nicotine-receptor occupancy."

The researchers noted that even the denicotinized cigarettes, which contained only trace amounts of the drug, still had enough nicotine to fill a quarter of the receptor sites in the brain.

Light cigarettes contain 0.6-1.0 milligrams of nicotine and regular cigarettes contain 1.2 to 1.4 milligrams of nicotine.

The findings were published online in the Aug. 18, 2008 issue of the International Journal of Neuropsychopharmacology.