High resolution autoradiographic determination of the topographic distribution of radioactivity in the hippocampal formation after injection of [1- 14C]glucose or 2-deoxy[ 14C]glucose

Abstract

Using high resolution autoradiography, the accumulation of radioactivity after intravenous injection of [1- 14C]glucose was measured in the corpus callosum, hippocampus, dorsal hippocampal commissure, somatosensory cortex, inferior colliculus and pontine periaqueductal grey. Autoradiograms were prepared by thaw-mounting 4μm frozen sections on nuclear emulsion-coated slides, and were evaluated quantitatively with a computer-assisted video system for automated counting of silver grains. In all brain regions examined, silver grain densities were greater in rats killed 30 min after injection of [1- 14C]glucose compared to rats killed 10 min after injection. After intravenous injection of [1- 14C]glucose or 2-deoxy[ 14C]glucose, the relative uptake and retention of radioactivity in different hippocampal subregions was compared. Striking differences were found in the hippocampus between 2-deoxy[ 14C]glucose and [1- 14]glucose autoradiograms. After injection of 2-deoxy[ 14C]glucose, there were large variations in the uptake and retention of radioactivity among different pyramidal cell fields. The CA 3 pyramidal cell field retained considerably more radioactivity than other pyramidal cell fields after injection of 2-deoxy[ 14C]glucose, while after injection of [1- 14C]glucose, the retention of radioactivity was similar in all pyramidal cell fields. After [1- 14C]glucose injection, the dentate gyrus contained relatively high levels of radioactivity and more 14C accumulated in the granular layer, compared to the molecular layer. In contrast, after 2-deoxy[ 14C]glucose injection, there was uniformly less radioactivity throughout the dentate gyrus when compared to rats injected with [1- 14C]glucose and there was no preferential accumulation of 2-deoxy[ 14C]glucose in the granular layer compared to the molecular layer. These results imply that, in the hippocampal formation, different cellular functions are assessed by the determination of the uptake and retention of radioactivity from [1- 14C]glucose and 2-deoxy[ 14C]glucose.