Difference in the uptake of glucose in various hippocampal regions

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By freeze-mount microautoradiography, differences in the uptake of tracers from radioactive 2-deoxyglucose ([1,2-^3H],[2,6-^3H]) and glucose ([1-^3H],[3-^3H]) into hippocampal regions were investigated after 45 minutes for 2-deoxyglucose(2-DG), and 15 and 45 minutes for glucose. Silver grains were assessed quantitatively by the image analyzer.(1) The radioactivity (silver grains/mm^2) in the stratum lacunosum-moleculare of the Ammon's horn from 2-DG autoradiograms was significantly higher than that of other hippocampal regions (p<0.01), while lowest in the hilus fascia dentata (p<0.01).(2) autoradiograms of [1-^3H] glucose and 15-min of [3-^3H] glucose showed that the radioactivity in the dentata molecular layer was significantly higher than that of other regions, expect for the stratum lacunosum-moleculare (p<0.05).(3) The 2-DG and 45-min glucose autoradiograms showed the intensely labeled perikarya of pyramidial cells in the CA3a sector.(4) Radioactivity in the dentate granular layer from 45-min autoradiogram of [3-^3H] glucose was significantly higher than that of the molecular layer (p<0.05).These results imply that the metabolic fate of glucose, i.e., whether it is mainly used for energy production or amino acid synthesis depends on each structure of the hippocampus. On the other hand, in order to investigate the factors responisible for glucose uptake, districution of synapses and GFA-positive glia in each hippocampal region was quantitatively observed using immnohistochemical preparations. As the results it was found that the radioactivity from 2-DG autoradiograms was closely related to the distribution of GFA-positive glia. i.e. the higher the grain density on an autoradiogram, the greater the glial density in that region.