EFFECTS OF ACETYLCHOLINE ON THE IN CORPORATION OF [32P]ORTHOPHOSPHATE IN VITRO INTO THE PHOSPHOLIPIDS OF SUBSYNAPTOSOMAL MEMBRANES FROM GUINEA-PIG BRAIN |
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Authors: | Y Yagihara J E Bleasdale J N Hawthorne |
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Institution: | Department of Biochemistry, University of Birmingham, England and Department of Chemistry, University of Calgary, Canada |
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Abstract: | -Synaptosomes prepared from guinea-pig cerebral cortex were incubated with 32P1 in a medium with or without 10?4 M-acetylcholine and 10?4 M-eserine. They were then subjected to osmotic shock and density-gradient centrifugation for the preparation of subsynaptosomal fractions and the phospholipids of each fraction were separated by two-dimensional thin-layer chromatography. The fraction containing synaptic vesicles and that containing mitochondria were the most highly labelled of the sub-synaptosomal fractions. Phosphatidic acid followed by phosphatidylinositol had the highest specific activity of the phospholipids studied. Acetylcholine caused a marked increase in the specific activity of the vesicular but not of the mitochondrial phosphatidic acid. Phosphatidylinositol specific activity also increased in the presence of acetylcholine but the increase was more reproducible in the fraction containing microsomal membranes than in the vesicle fraction. The other phospholipids were relatively poorly labelled and no effect of acetylcholine on the incorporation of 32P1 into these lipids could be detected. Acetylcholine also caused a decrease in the amount of phosphatidic acid in the synaptic vesicles. |
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