受動喫煙だけでもニコチン依存症になる恐れ有り

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2011年07月04日(Mon) 18:22 by drharasho

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Effect of Secondhand Smoke on Occupancy of Nicotinic Acetylcholine
Receptors in Brain

Arthur L. Brody, MD; Mark A. Mandelkern, MD, PhD; Edythe D. London, PhD;
Aliyah Khan, BS; Daniel Kozman, BS; Matthew R. Costello, BA;
Evan E. Vellios, BS; Meena M. Archie, BS; Rebecca Bascom, MD;
Alexey G. Mukhin, MD, PhD

Arch Gen Psychiatry. Published online May 2, 2011. doi:10.1001/
archgenpsychiatry.2011.51

Context
 Despite progress in tobacco control, secondhand smoke (SHS)
exposure remains prevalent worldwide and is implicated in the initiation
and maintenance of cigarette smoking.

Objective 
To determine whether moderate SHS exposure results in brain
 α4β2* nicotinic acetylcholine receptor (nAChR) occupancy.

Design, Setting, and Participants 
Positron emission tomography scanning
 and the radiotracer 2-[18F]fluoro-3-(2(S)azetidinylmethoxy) pyridine
 (also known as 2-[18F]fluoro-A-85380, or 2-FA) were used to determine
α4β2* nAChR occupancy from SHS exposure in 24 young adult participants
(11 moderately dependent cigarette smokers and 13 nonsmokers).
Participants underwent two bolus-plus-continuous-infusion 2-FA positron
emission tomography scanning sessions during which they sat in the
passenger's seat of a car for 1 hour and either were exposed to moderate
 SHS or had no SHS exposure. The study took place at an academic
positron emission tomography center.

Main Outcome Measure 
Changes induced by SHS in 2-FA specific binding
volume of distribution as a measure of α4β2* nAChR occupancy.

Results
 An overall multivariate analysis of variance using specific
binding volume of distribution values revealed a significant main effect
 of condition (SHS vs control) (F1,22 = 42.5, P < .001) but no
between-group (smoker vs nonsmoker) effect. Exposure to SHS led to
a mean 19% occupancy of brain α4β2* nAChRs (1-sample t test, 2-tailed,
 P < .001). Smokers had both a mean 23% increase in craving with SHS
 exposure and a correlation between thalamic α4β2* nAChR occupancy
and craving alleviation with subsequent cigarette smoking (Spearman
{rho} = –0.74, P = .01).

Conclusions
 Nicotine from SHS exposure results in substantial brain
 α4β2* nAChR occupancy in smokers and nonsmokers. Study findings
suggest that such exposure delivers a priming dose of nicotine to
the brain that contributes to continued cigarette use in smokers.

This study has implications for both biological research into the link
 between SHS exposure and cigarette use and public policy regarding
the need to limit SHS exposure in cars and other enclosed spaces.


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