Typical smokers need to have brain nicotine receptors almost completely saturated throughout the day. This need creates an almost uncontrollable urge to keep smoking, commented Nora D. Volkow, MD, director of the National Institute on Drug Abuse (NIDA), addressing a study by NIDA researchers on nicotine addiction.
Typical smokers need to have brain nicotine receptors almost completely saturated throughout the day. This need creates an almost uncontrollable urge to keep smoking, commented Nora D. Volkow, MD, director of the National Institute on Drug Abuse (NIDA), addressing a study by NIDA researchers on nicotine addiction. "The study illustrates the powerfully addictive impact of even small amounts of nicotine," she said.
A team from the University of California, Los Angeles (UCLA) David Geffen School of Medicine used positron emission tomography (PET) to observe nicotine distribution in the brains of 11 smokers. Participants had to choose between not smoking, having 1 puff, 3 puffs, 1 full cigarette, or smoking until their craving was satisfied. The team, led by Arthur Brody, MD, associate professor in the Department of Psychiatry and Biobehavioral Sciences at UCLA, measured craving using the Urge to Smoke scale, which assesses responses to 10 craving-related questions. They also used MRI to help localize brain regions on the PET scans.
The researchers found that the amount of nicotine contained in just 1 puff can occupy about 30% of α4ß2*nicotinic acetylcholine receptors (nAChRs), while 3 puffs of a cigarette can occupy about 70% of them. The smoker becomes temporarily satisfied when nearly all the receptors are occupied, usually after smoking at least 2.5 cigarettes. Soon, however, satiation wears off, driving the smoker to continue smoking throughout the day to satisfy cravings.
A more complete understanding of how nicotine affects the brain can help scientists develop better therapies for cigarette smokers who want to quit. The study was published in the August 2006 issue of the Archives of General Psychiatry. The citation for the study is: Brody AL, Mandelkern MA, London ED, et al. Cigarette smoking saturates brain alpha 4 beta 2 nicotinic acetylcholine receptors. Arch Gen Psychiatry. 2006;63:907-915.
Editor's Note: A version of this news brief appeared in the August 28, 2006, issue of Diagnosticimaging.com, the online weekly news bulletin of Diagnostic Imaging. The news brief has been revised and reformatted for Applied Neurology.