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Cigarette Smoking Saturates Brain 4 2 Nicotinic Acetylcholine Receptors
Arthur L. Brody, MD;
Mark A. Mandelkern, MD, PhD;
Edythe D. London, PhD;
Richard E. Olmstead, PhD;
Judah Farahi, PhD;
David Scheibal, BS;
Jennifer Jou, BS;
Valerie Allen, BS;
Emmanuelle Tiongson, BS;
Svetlana I. Chefer, PhD;
Andrei O. Koren, PhD;
Alexey G. Mukhin, MD, PhD
Arch Gen Psychiatry. 2006;63:907-914.
Context 2-[18F]fluoro-3-(2(S)-azetidinylmethoxy) pyridine (2-F-A-85380, abbreviated as 2-FA) is a recently developed radioligand that allows for visualization of brain 4 2* nicotinic acetylcholine receptors (nAChRs) with positron emission tomography (PET) scanning in humans.
Objective To determine the effect of cigarette smoking on 4 2* nAChR occupancy in tobacco-dependent smokers.
Design Fourteen 2-FA PET scanning sessions were performed. During the PET scanning sessions, subjects smoked 1 of 5 amounts (none, 1 puff, 3 puffs, 1 full cigarette, or to satiety [2 to 3 cigarettes]).
Setting Academic brain imaging center.
Participants Eleven tobacco-dependent smokers (paid volunteers).
Main Outcome Measure Dose-dependent effect of smoking on occupancy of 4 2* nAChRs, as measured with 2-FA and PET in nAChR-rich brain regions.
Results Smoking 0.13 (1 to 2 puffs) of a cigarette resulted in 50% occupancy of 4 2* nAChRs for 3.1 hours after smoking. Smoking a full cigarette (or more) resulted in more than 88% receptor occupancy and was accompanied by a reduction in cigarette craving. A venous plasma nicotine concentration of 0.87 ng/mL (roughly 1/25th of the level achieved in typical daily smokers) was associated with 50% occupancy of 4 2* nAChRs.
Conclusions Cigarette smoking in amounts used by typical daily smokers leads to nearly complete occupancy of 4 2* nAChRs, indicating that tobacco-dependent smokers maintain 4 2* nAChR saturation throughout the day. Because prolonged binding of nicotine to 4 2* nAChRs is associated with desensitization of these receptors, the extent of receptor occupancy found herein suggests that smoking may lead to withdrawal alleviation by maintaining nAChRs in the desensitized state.
Author Affiliations: Department of Psychiatry and Biobehavioral Sciences (Drs Brody and London, Mr Scheibal, and Mss Jou, Allen, and Tiongson), University of California, Los Angeles; Greater Los Angeles Veterans Affairs Healthcare System Positron Emission Tomography Center (Drs Brody, Mandelkern, London, Olmstead, and Farahi, Mr Scheibal, and Mss Jou, Allen, and Tiongson), Los Angeles; Department of Physics, University of California, Irvine (Dr Mandelkern); Intramural Research Program, Neuroimaging Research Branch, National Institute on Drug Abuse, Rockville, Md (Drs Chefer and Mukhin); and Institute for Neurodegenerative Disorders, New Haven, Conn (Dr Koren).
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