title: Damage to the high-affinity ?-aminobutyric acid (GABA) uptake system in mouse brain by horseradish peroxidase (HRP).
abstract: Presynaptic nerve terminals when depolarized are sensitive to morphological and functional alteration by horseradish peroxidase. Mouse brain slices, 0.1 mm, depolarized by a K(+)-HEPES buffer and exposed to horseradish peroxidase exhibited alterations in both synaptic vesicle membrane structure and in high-affinity [(14)C]?-aminobutyric acid uptake. The post stimulatory retrieval of synaptic vesicles from the nerve terminal plasma membrane in the presence of horseradish peroxidase resulted in a decrease in the synaptic vesicle population with a concurrent increase in non-synaptic vesicle membrane structures. High-affinity [(14)C]?-aminobutyric acid uptake into 0.1-mm slices of mouse cerebral cortex and ponsmedulla-spinal cord was inhibited by 31% and 24%, respectively, after incubation for 60 min in K(+)-HEPES buffer containing horseradish peroxidase. Superoxide dismutase protected both the synaptic vesicle membrane and the high-affinity uptake system from the deleterious effects of horseradish peroxidase, pointing to the possible involvement of superoxide anion radicals in the horseradish peroxidase-related effects. These horseradish peroxidase induced alterations appear to be directed towards the exposed synaptic vesicle membrane, since non-stimulated brain slices exposed to horseradish peroxidase do not exhibit a reduction in either high- or low-affinity [(14)C]?-aminobutyric acid uptake. Low-affinity uptake of [(14)C]?-aminobutyric acid and [(14)C]?-aminoisobutyric acid into cortical slices was not affected after incubation in K(+)-HEPES with horseradish peroxidase. Low-affinity uptake, however, is reduced by the high-K(+)/Na(+)-free stimulatory incubation prior to uptake. It appears, thus, that high- and low-affinity uptake are distinct and different systems, with the high-affinity transport system structurally associated with synaptic vesicle membrane.
authors.affiliation: Center for Neurochemistry, The Nathan S. Kline Institute for Psychiatric Research, Ward's Island, New York, NY 10035, U.S.A.
authors.forename: E A
authors.initials: EA
authors.lastname: Debler
authors.forename: H
authors.initials: H
authors.lastname: Sershen
authors.forename: A
authors.initials: A
authors.lastname: Lajtha
authors.forename: J F
authors.initials: JF
authors.lastname: Gennaro