AMINO-ACID-CONCENTRATIONS AND SELECTED ENZYME-ACTIVITIES IN RAT AUDITORY, OLFACTORY, AND VISUAL SYSTEMS

Homogenates of specific brain regions of three sensory systems (audito ry, olfactory, and visual) were prepared from pigmented Long-Evans Hoo ded rats and assayed for amino acid concentrations and activities of g lutaminase, aspartate aminotransferase (total, cytosolic, and, by diff erence, mitochondrial), malate dehydrogenase, lactate dehydrogenase, a nd choline acetyltransferase. Comparing the quantitative distributions among regions revealed significant correlations between AAT and aspar tate, between glutaminase and glutamate, between glutamate and glutami ne, and between AAT plus glutaminase, or glutaminase alone, and the su m of aspartate, glutamate, and GABA, suggesting a metabolic pathway in volving the synthesis of a glutamate pool as precursor to aspartate an d GABA. Of the inhibitory transmitter amino acids, GABA concentrations routinely exceeded those of glycine, but glycine concentrations were relatively high in brainstem auditory structures.