Tritiated 2‐deoxy‐D‐glucose: A high‐resolution marker for autoradiographic localization of brain metabolism

The technique for autoradiographic localization of 2‐deoxy‐D‐glucose (2DG) uptake has become a useful method for observing alterations of functional brain activity resulting from experimental manipulation. Autoradiographic resolution is improved using tritiated ([ 3 H]) rather than carbon‐14 ([ 14 C])2DG, due to the lower energy and shorter path of tritium emissions. In addition, lower 2DG uptake by white matter relative to gray matter is exaggerated in the [ 3 H]2DG autoradiographs due to the greater absorption of tritium emissions by lipids. Using [ 3 H]2DG, it is possible to observe differential metabolic labeling in various individual nuclei or portions of nuclei that is unresolvable using [ 14 C]2DG in the awake, normal animal. Heterogeneous patterns of 2DG uptake seen only with [ 3 H]2DG are found in the nucleus accumbens, the anterior portion of the basolateral nucleus of the amygdala, specific nuclei of the inferior olivary complex, various hypothalamic regions, and a region straddling the border of the medial and lateral habenular nuclei. The lamination of differential 2DG uptake in the hippocampus is better localized using [ 3 H]2DG. Autoradiographic resolution of labeled 2DG is further improved when the brain is perfused prior to frozen sectioning, due perhaps to selective fixation and retention of intracellular labeled 2‐deoxy‐glycogen. A series of [ 3 H]2DG autoradiographs are presented together with views of the Nissl‐stained sections that produced the autoradiographs.