主页 > 医学前沿 >
【bio-news】吸烟改变大脑化学组成
11/28/06 -- Chronic smoking affects nerve cells and alters the chemical makeup of the brain, according to research presented today at the annual meeting of the Radiological Society of North America (RSNA).
"This is the first imaging study to focus on the relationship between brain metabolites and nicotine dependence," said Okan Gür, M.D., from the Department of Radiology at the University of Bonn in Germany.
Dr. Gür and colleagues used proton magnetic resonance spectroscopy (MRS) to study 21 men and 22 women, age 21 to 59, in a smoking cessation program two weeks after quitting and again six months later. Patients were encouraged to use nicotine patches during the initial six weeks of smoking cessation; however, only 36 of the patients complied.
Proton MRS is able to measure brain metabolism at the cellular level and can provide detailed chemical data about the brain's metabolites, which are involved in many physical and chemical processes within the body.
The researchers compared the data collected from the smokers to proton MRS data collected from 35 age- and gender-matched healthy controls.
The results showed that the nicotine-dependent patients had significantly decreased concentrations of the amino acid N-acetylaspartate (NAA) in the anterior cingulate cortex (ACC), the part of the brain that processes pleasure and pain. The decreased NAA levels were evident regardless of whether or not the patient used a nicotine patch and correlated directly with the patient's smoking history: the greater the number of pack years (one pack per day for one year equals one pack year), the lower the NAA level.
"The ACC is involved in mediating conditioned reinforcement, craving and relapsing behavior in addiction," said study co-author Christian G. Schütz, M.D., M.P.H., from the Department of Psychiatry at the University of Bonn. "Lower NAA levels have been implicated as indicators of neuronal or axonal dysfunction."
Reduced NAA levels have been reported for a number of psychiatric and mood disorders, including schizophrenia, dementia and bipolar disorder, as well as in cases of substance abuse, particularly alcohol dependence.
Choline concentrations in the ACC were slightly lower in the smokers compared with the nonsmokers, and lower still in the female smokers compared with the male smokers.
Choline is significantly involved in cell membrane metabolism, which is essential for cardiac and brain function. Reduced choline levels can be a precursor to the breakdown of cell membranes.
Concentration of total creatine (tCr) levels in the frontal lobes was typically higher in the smokers who did not use patches compared to those who did. The metabolite tCr plays an important role in supplying energy to the muscle cells. Higher tCr levels have been associated with stimulant use. Furthermore, the researchers found that high tCr levels predicted a higher likelihood of relapse.
Upon follow-up after six months, the researchers found that most metabolite concentrations, including that of NAA, had normalized in the 25 ex-smokers who did not relapse.
"These findings further emphasize the importance of quitting smoking," Dr. Gür said. "The degree of reduction of NAA in the ACC depends on the amount of tobacco consumed over time, but it appears to normalize after smoking cessation."
Source: Radiological Society of North America
http://www.bio.com/newsfeatures/newsfeatures_research.jhtml;jsessionid=RIYDWYGEBU20NR3FQLMSFEWHUWBNQIV0?cid=24000022 本人已认领该文编译，48小时后若未提交译文，请其他战友自由认领。
吸烟会改变大脑的化学组成
在本年度北美放射学会年会上发表的一项研究结果表明：长期吸烟会影响到神经细胞进而改变大脑的化学组成。德国波恩大学放射学系的 Okan Gür博士说：这是着眼于大脑代谢产物与尼古丁依赖之间的关系的第一项影响学研究。
Gür博士与他的团队利用磁共振质子波谱对年龄在21岁到59岁之间的21名男性受试者与22名女性受试者进行了测试，按照计划安排，第一次测试在停止吸烟两周之后，下一次则在戒烟六个月之后，在停止吸烟的头六周之内鼓励受试者使用尼古丁的替代品来帮助戒烟；最后只有36名受试者完成了整个测试。
磁共振质子波谱可以在细胞水平测定脑内代谢并可以提供详尽的脑内代谢物的化学组成成分的数据，这些成分与体内的多个物理与化学反应过程相关。
研究者把35名吸烟者的磁共振质子波谱数据与相应的在年龄与性别上都可以匹配的健康对照的数据进行了比较。结果表明尼古丁依赖患者的前扣带回皮质的N-乙酰天冬酰胺水平显著下降，扣带回主要与欣快感与痛觉有关。N-乙酰天冬酰胺的下降程度与是否应用尼古丁替代品几乎无关，主要与患者的烟龄有关。包年（所谓包年指的是一年内每天一包烟称为一个包年）的数目越大，相应的N-乙酰天冬酰胺水平越低。
阅读本文的人还阅读：
作者:admin@医学,生命科学 2011-04-25 05:11
医学,生命科学网