Glial contribution to amino acid content and metabolism of the deafferented dentate gyrus.

Abstract

The time course of tissue content and evoked release of endogenous amino acids was analyzed in the partially deafferented dentate gyrus of the rat hippocampus 2-24 days following unilateral lesion of the perforant path. Amino acids in tissue extracts and perfusates were determined after precolumn derivatization and hplc separation. The astrocytic glial cell reaction was monitored with immunohistochemistry of S-100. The tissue content of glutamate decreased significantly on the lesioned side, whereas only a moderate reduction in taurine, aspartate, and alanine occurred. Glutamine was significantly elevated at 7 days. The evoked efflux of glutamate was reduced at 2 and 7 days, whereas no change was seen at longer survival periods. The evoked release of GABA and aspartate increased on the denervated side after 12 and 24 days. The rate of carbon utilization into amino acid pools was followed with 14C-glucose and 14C-acetate. The incorporation of acetate showed a peak 2-9 days following lesion, which paralleled in time the hypertrophic glial cells. The incorporation of glucose decreased during this period. The metabolic events are discussed in relation to the morphological changes in synapses and glial cells.