Premium
Uptake of γ‐Aminobutyric Acid by Brain Tissue Preparations: A Reevaluation
Author(s) -
Wood J. D.,
Sidhu H. S.
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb13034.x
Subject(s) - aminobutyric acid , incubation , extracellular , gamma aminobutyric acid , chemistry , cerebral cortex , biophysics , biochemistry , biology , endocrinology , receptor
The kinetic constants K m and V max for the uptake of γ‐aminobutyric acid (GABA) by various preparations from rat cerebral cortex were determined by means of Eadie‐Hofstee plots and computer analysis. The K m values were much greater in 0.1‐mm slices than in synaptosomal preparations, and the K m value increased further with the thickness of the slices. The apparent high K m values in slices were probably due to depletion of the GABA concentration in the extracellular fluid as the exogenous GABA ran the gauntlet of competing uptake sites on its way to sites deep within the slice, thereby bringing about a requirement for higher GABA concentrations in the incubation medium in order to maintain the internal GABA levels at the “ K m level.” Evidence was obtained for three GABA uptake systems with K m values (in synaptosomes) of 1.1 μ M , 43 μ M , and 3.9 m M , respectively. In contrast, only two uptake systems for d ‐aspartate were detected, with k m values of 1.8 μ M and 1.8 m M , respectively. The implications of the findings in the study with respect to previous data in the literature are discussed.