Regional cerebral blood flow effects of nicotine in overnight abstinent smokers

Background: Most people agree that dependence to tobacco is mediated by the effects of nicotine on the central nervous system, albeit the neural pathways involved are not clearly delineated. We investigated the effect of nasal nicotine spray on regional cerebral blood flow (rCBF) in a sample of habitual smokers, with H215O and positron emission tomography (PET). Methods: Eighteen volunteer smokers were studied after 12 hours of smoking deprivation. Regional cerebral blood flow measures were obtained with PET and 50 mCi H215O in six consecutive scans. Nicotine spray and a placebo spray were administered in a single-blind design, preceded and followed by baseline studies. Images were coregistered and anatomically standardized. Square (9-mm side) regions of interest were placed in 10 preselected brain regions, bilaterally. The effects of the experimental condition and gender were tested with two-way repeated-measures analysis of variance in each of the regions studied. Results: Nicotine reduced rCBF in the left anterior temporal cortex and in the right amygdala. Increases were noted in the right anterior thalamus. Conclusions: In habitual smokers after overnight abstinence, nicotine induced differing effects on regional blood flow relative to whole brain blood flow. Increases were observed in the thalamus, a region rich in nicotinic receptors, and reductions in limbic and paralimbic (amygdala, anterior temporal cortex) regions.