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Arch Gen Psychiatry:大麻对人脑的影响有利有弊

2012/01/21 来源:搜狐
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导读
大麻是可导致精神恍惚的毒品原料植物,早有研究显示长期吸食大麻可导致精神疾病。英国一项最新研究却显示,大麻中两种主要成分对大脑的影响互相克制,其中一种成分可以导致精神病,而另一种成分或许可用于治疗精神病。

大麻是可导致精神恍惚的毒品原料植物,早有研究显示长期吸食大麻可导致精神疾病。英国一项最新研究却显示,大麻中两种主要成分对大脑的影响互相克制,其中一种成分可以导致精神病,而另一种成分或许可用于治疗精神病。

英国伦敦国王学院等机构研究人员在新一期学术刊物《普通精神病学文献》上报告说,他们以大麻的两种主要成分四氢大麻酚和大麻二酚为对象进行了研究,让一些大麻吸食者每次单独摄入其中一种物质,然后用磁共振成像技术观察他们大脑出现的变化,还让他们接受了一些认知方面的测试。

结果显示,四氢大麻酚会增强大脑中纹状体等区域的活性,并削弱另一些大脑区域的活性。其结果是,大麻吸食者对一些不怎么重要的外界刺激的反应强度增加,而对一些通常看来重要的外界刺激的反应减弱。这也解释了为什么吸食大麻会让人精神恍惚,长期吸食还会使人对各种事物的判断错乱,导致精神疾病。

但研究还发现,大麻二酚可以起到一定程度上与四氢大麻酚相反的效果。对于活性受到四氢大麻酚削弱的一些大脑区域,大麻二酚可以增强这些区域的活性。

研究人员说,这些发现帮助加深了对大麻作用机制的了解。一方面,研究显示了四氢大麻酚与精神疾病之间的关系,现在一些地方的大麻毒品中四氢大麻酚的含量越来越高,是让人担心的事情;而另一方面,研究结果也说明大麻二酚或许可以增强这些区域的活性。


Induction of Psychosis by 9-Tetrahydrocannabinol Reflects Modulation of Prefrontal and Striatal Function During Attentional Salience Processing

Sagnik Bhattacharyya, MBBS, MD, PhD; José Alexandre Crippa, MD, PhD; Paul Allen, PhD; Rocio Martin-Santos, MD, PhD; Stefan Borgwardt, PhD; Paolo Fusar-Poli, MD; Katya Rubia, PhD; Joseph Kambeitz, MB; Colin O’Carroll, PhD; Marc L. Seal, PhD; Vincent Giampietro, PhD; Michael Brammer, PhD; Antonio Waldo Zuardi, MD, PhD; Zerrin Atakan, MD, FRCPsych; Philip K. McGuire, MD, PhD 

Context  The aberrant processing of salience is thought to be a fundamental factor underlying psychosis. Cannabis can induce acute psychotic symptoms, and its chronic use may increase the risk of schizophrenia. We investigated whether its psychotic effects are mediated through an influence on attentional salience processing.

Objective  To examine the effects of 9-tetrahydrocannabinol (9-THC) and cannabidiol (CBD) on regional brain function during salience processing.

Design  Volunteers were studied using event-related functional magnetic resonance imaging on 3 occasions after administration of 9-THC, CBD, or placebo while performing a visual oddball detection paradigm that involved allocation of attention to infrequent (oddball) stimuli within a string of frequent (standard) stimuli.

Results  During the processing of oddball stimuli, relative to placebo, 9-THC attenuated activation in the right caudate but augmented it in the right prefrontal cortex. 9-Tetrahydrocannabinol also reduced the response latency to standard relative to oddball stimuli. The effect of 9-THC in the right caudate was negatively correlated with the severity of the psychotic symptoms it induced and its effect on response latency. The effects of CBD on task-related activation were in the opposite direction of those of 9-THC; relative to placebo, CBD augmented left caudate and hippocampal activation but attenuated right prefrontal activation.

Conclusions  9-Tetrahydrocannabinol and CBD differentially modulate prefrontal, striatal, and hippocampal function during attentional salience processing. These effects may contribute to the effects of cannabis on psychotic symptoms and on the risk of psychotic disorders.

文献链接:http://archpsyc.ama-assn.org/cgi/content/abstract/69/1/27?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=tetrahydrocannabinol+&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT

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