GABA TRANSPORT BY NERVE ENDING FRACTIONS OF CAT BRAIN¹

Nerve ending and mitochondrial fractions were prepared from cat cerebral cortex by differential and sucrose density gradient centrifugation and the nerve‐ending fraction was shown to be particularly rich in glutamate decarboxylase activity.

Abstract

Abstract— Nerve ending and mitochondrial fractions were prepared from cat cerebral cortex by differential and sucrose density gradient centrifugation. The isolated fractions were characterized morphologically and enzymatically and the nerve‐ending fraction was shown to be particularly rich in glutamate decarboxylase activity. The uptake of [ 3 H] γ‐aminobutyric acid (GABA) was studied by trapping the particles on a Millipore filter. GABA uptake was not saturable over the concentration range studied (0.018 to 8000 μM. Tissue/medium ratios were consistently greater than 2·5, and uptake was significantly reduced by ouabain and iodoacetate, or by replacing sodium with lithium or choline chloride. GABA uptake was significantly inhibited by desmethylimipramine (DMI) with an IC 50 of approx. 10–20 μM. GABA uptake was reduced by structurally similar amino acids lacking an α‐amino group, and also by methionine and phenylalanine, but not by short chain neutral amino acids.