Leibniz Institut für Neurobiologie, Abteilung Akustik LernenSprache, Brenneckestrasse 6, Magdeburg, Germany.
Neuroimage. 2010 Jan 1;49(1):303-15. doi: 10.1016/j.neuroimage.2009.08.012. Epub 2009 Aug 12.
In neurons the rate of K(+)-uptake increases with increasing activity. K(+)-analogues like the heavy metal ion thallium (Tl(+)) can be used, therefore, as tracers for imaging neuronal activity. However, when water-soluble Tl(+)-salts are injected systemically only minute amounts of the tracer enter the brain and the Tl(+)-uptake patterns are influenced by regional differences in blood-brain barrier (BBB) K(+)-permeability. We here show that the BBB-related limitations in using Tl(+) for imaging neuronal activity are no longer present when the lipophilic Tl(+) chelate complex thallium diethyldithiocarbamate (TlDDC) is applied. We systemically injected rodents with TlDDC and mapped the Tl(+)-distribution in the brain using an autometallographic (AMG) technique, a histochemical method for detecting heavy metals. We find that Tl(+)-doses for optimum AMG staining could be substantially reduced, and regional differences attributable to differences in BBB K(+)-permeability were no longer detectable, indicating that TlDDC crosses the BBB. At the cellular level, however, the Tl(+)-distribution was essentially the same as after injection of water-soluble Tl(+)-salts, indicating Tl(+)-release from TlDDC prior to neuronal or glial uptake. Upon sensory stimulation or intracortical microstimulation neuronal Tl(+)-uptake increased after TlDDC injection, upon muscimol treatment neuronal Tl(+)-uptake decreased. We present a protocol for mapping neuronal activity with cellular resolution, which is based on intravenous TlDDC injections during ongoing activity in unrestrained behaving animals and short stimulation times of 5 min.
在神经元中，K(+)摄取速率随活动的增加而增加。因此，可以使用 K(+)类似物，如重金属离子铊（Tl(+)），作为神经元活动成像的示踪剂。然而，当水溶性 Tl(+)盐系统注射时，只有微量的示踪剂进入大脑，并且 Tl(+)摄取模式受血脑屏障（BBB）K(+)通透性的区域差异影响。我们在这里表明，当使用亲脂性 Tl(+)螯合物复合物二乙基二硫代氨基甲酸盐（TlDDC）时，用于成像神经元活动的 Tl(+)的 BBB 相关限制不再存在。我们系统地给啮齿动物注射 TlDDC，并使用自动金属照相术（AMG）技术，一种用于检测重金属的组织化学方法，绘制大脑中的 Tl(+)分布。我们发现，最佳 AMG 染色的 Tl(+)剂量可以大大降低，并且归因于 BBB K(+)通透性差异的区域差异不再可检测，表明 TlDDC 穿过 BBB。然而，在细胞水平上，Tl(+)分布与注射水溶性 Tl(+)盐后基本相同，表明 Tl(+)在被神经元或神经胶质摄取之前从 TlDDC 中释放。在感觉刺激或皮质内微刺激后，注射 TlDDC 后神经元 Tl(+)摄取增加，而在 muscimol 处理后神经元 Tl(+)摄取减少。我们提出了一种基于静脉内 TlDDC 注射在未受约束的行为动物中进行的、具有细胞分辨率的映射神经元活动的方案，以及持续活动和 5 分钟的短刺激时间。
