Abnormal hippocampal neurochemistry in smokers: evidence from proton magnetic resonance spectroscopy at 3 T.
OBJECTIVE
In animals, nicotine, the primary psychoactive constituent of tobacco smoke, reduces neurogenesis and increases cell loss in both hippocampus and cortex. Accordingly, tobacco smoking has been linked to reduced performance on cognitive paradigms requiring attention and working memory in humans. However, few prior studies have tested for evidence of structural brain alterations in human tobacco smokers. In this study, proton magnetic resonance spectroscopy was used to assess the effects of chronic smoking on neuronal integrity of the hippocampus and anterior cingulate cortex (ACC).


METHODS
Absolute concentrations of N-acetylaspartate, total choline (tCho), and total creatine were measured in the left hippocampus and ACC in 13 chronic tobacco smokers and 13 nonsmokers matched for age, sex, and education.


RESULTS
The N-acetylaspartate concentration was significantly reduced in smokers relative to nonsmokers in the left hippocampus but not in the ACC. There were no group differences in the tCho and total creatine concentrations in either voxel. However, ACC tCho concentration was positively correlated with magnitude of lifetime exposure to tobacco smoke (pack-years).


CONCLUSIONS
The results are consistent with prior observations of hippocampal neuronal damage in rodents receiving nicotine and working memory deficits in human tobacco smokers. The positive relationship between tCho and lifetime tobacco exposure suggests that a component of tobacco smoke, presumably nicotine, may increase cortical membrane turnover or modify cell density. Together, these results add to growing evidence that nicotine exerts neurotoxic effects in human brain, although an a priori nature of the findings cannot be ruled out.
Gallinat
Jürgen
J
Klinik für Psychiatrie und Psychotherapie, Charité Universitätsmedizin, Campus Mitte (PUK Charité SHK), Berlin, Germany. juergen.gallinat@charite.de
Lang
Undine E
UE
Jacobsen
Leslie K
LK
Bajbouj
Malek
M
Kalus
Peter
P
von Haebler
Dorothea
D
Seifert
Frank
F
Schubert
Florian
F
D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D016022:Case-Control Studies; D002794:Choline / Q000378:metabolism*; D003401:Creatine / Q000378:metabolism*; D005260:Female; D006179:Gyrus Cinguli / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000378:metabolism*
D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline