THE UPTAKE OF [3H]GABA BY SLICES OF RAT CEREBRAL CORTEX |
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Authors: | L L Iversen M J Neal |
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Institution: | Department of Pharmacology, University of Cambridge, Cambridge, England |
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Abstract: | —A rapid accumulation of 3H]GABA occurs in slices of rat cerebral cortex incubated at 25° or 37° in a medium containing 3H]GABA. Tissue medium ratios of almost 100:1 are attained after a 60 min incubation at 25°. At the same temperature no labelled metabolites of GABA were found in the tissue or the medium. The process responsible for 3H]GABA uptake has many of the properties of an active transport mechanism: it is temperature sensitive, requires the presence of sodium ions in the external medium, is inhibited by dinitrophenol and ouabain, and shows saturation kinetics. The estimated Km value for GABA is 2·2 × 10?5m , and Vmax is 0·115 μmoles/min/g cortex. There is only negligible efflux of the accumulated 3H]GABA when cortical slices are exposed to a GABA-free medium. 3H]GABA uptake was not affected by the presence of large molar excesses of glycine, l -glutamic acid, l -aspartic acid, or β-aminobutyrate, but was inhibited in the presence of l -alanine, l -histidine, β-hydroxy-GABA and β-guanidinopropionate. It is suggested that the GABA uptake system may represent a possible mechanism for the inactivation of GABA or some related substance at inhibitory synapses in the cortex. |
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