Freeze-mount microautoradiographic study in the mouse hippocampus after intravenous injection of tritiated 2-deoxyglucose and glucose

Differences in the uptake of tracers from radioactive 2-deoxyglucose ([1,2-3H] and [2,6-3H]), and glucose ([1-3H], [3-3H]) into hippocampal regions were investigated by freeze-mount microautoradiography after 45 min for 2-deoxyglucose, and after 15 and 45 min for glucose. Silver grains were assessed quantitatively by an image analyser. (1) The radioactivity (silver grains/mm2) in the stratum lacunosum-moleculare of Ammon's horn from 2-deoxyglucose autoradiograms was significantly higher than that in other hippocampal regions (P less than 0.01), while lowest in the hilus fascia dentata (P less than 0.01). (2) Autoradiograms of [1-3H]glucose and 15 min of [3-3H]glucose showed the radioactivity in the dentate molecular layer to be significantly higher than that in other regions, excepting the stratum lacunosummoleculare (P less than 0.05). (3) The 2-deoxyglucose and 45-min glucose autoradiograms showed intensely labeled perikarya of pyramidal cells in the CA3a sector. (4) Radioactivity in the dentate granular layer from the 45-min autoradiogram of [3-3H]glucose was significantly higher than that in the molecular layer (P less than 0.05). The 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.