Region-specific effects of a Trosine-Free amino acid mixture on amphetamine-induced changes in BOLD fMRI signal in the rat brain
Region-specific effects of a Trosine-Free amino acid mixture on amphetamine-induced changes in BOLD fMRI signal in the rat brain
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DOI：
10.1002/syn.20442
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发表时间：
2007-11-01
期刊：
影响因子：
2.3
通讯作者：
Sharp, Trevor
中科院分区：
文献类型：
--
作者：
Preece, Mark A.;Sibson, Nicola R.;Sharp, Trevor
背景资料：使用不含酪氨酸的氨基酸混合物急性消耗酪氨酸提供了一种新的饮食方法来抑制大脑中激活的多巴胺通路。本研究探讨了体内功能磁共振成像（fMRI）方法作为一种非侵入性手段来检测酪氨酸耗竭对多巴胺功能的影响。研究方法：通过给予多巴胺释放剂安非他明（3 mg/kg i. v.）诱导的血氧水平依赖性（BOLD）对比度的变化，在氟烷麻醉的大鼠中测量。结果如下：安非他明引起BOLD信号强度的变化，在丘脑核（-7.7%）、前额叶皮层（-13.6%）和运动皮层（+12.5%）中观察到最大的影响。用不含酪氨酸的氨基酸混合物预处理减弱了某些区域（丘脑核和前额叶皮层）对苯丙胺的反应，但其他区域（运动皮层）则没有。安非他明本身对丘脑和海马体没有影响，但令人惊讶的是，在氨基酸混合物后增加了BOLD信号。结论：这些实验表明，安非他明引起区域特定的变化，在大鼠的BOLD信号，这种影响是衰减在一些但不是所有地区的酪氨酸耗竭。这些数据支持应用功能磁共振成像技术研究酪氨酸耗竭对动物和人类多巴胺功能的影响。
Background: Acute depletion of tyrosine using a tyrosine-free amino acid mixture offers a novel dietary approach to inhibit activated dopamine pathways in the brain. This study investigated the potential of in vivo functional magnetic resonance imaging (fMRI) methods as a noninvasive means to detect effects of tyrosine depletion on dopamine function. Methods: Changes in blood-oxgenation level dependent (BOLD) contrast induced by administration of the dopamine-releasing agent, amphetamine (3 mg/kg i.v.), were measured in halothane-anaesthetised rats. Results: Amphetamine evoked changes in BOLD signal intensity with the greatest effects observed in the nucleus accumbens (-7.7%), prefrontal cortex (-13.6%), and motor cortex (+12.5%). Pretreatment with a tyrosine-free amino acid mixture attenuated the response to amphetamine in some regions (nucleus accumbens and prefrontal cortex), but not others (motor cortex). Amphetamine itself had no effect in thalamus and hippocampus but, surprisingly, increased the BOLD signal after the amino acid mixture. Conclusion: These experiments demonstrate that amphetamine evokes region-specific changes in the BOLD signal in rats, and that this effect is attenuated in some but not all regions by tyrosine depletion. The data support the application of fMRI techniques for studying the effects of tyrosine depletion on dopamine function in animals and also humans.