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Sodium‐Dependent Efflux of [ 3 H]GABA from Synaptosomes Probably Related to Mitochondrial Calcium Mobilization
Author(s) -
Sandoval Maria Elena
Publication year - 1980
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.1471-4159.1980.tb07090.x
Subject(s) - free nerve ending , efflux , egta , ouabain , sodium , synaptosome , chemistry , calcium , biophysics , mitochondrion , liberation , depolarization , ionophore , intracellular , biochemistry , incubation , endocrinology , biology , membrane , in vitro , organic chemistry
It has been suggested that mitochondria might modify transmitter release through the control of intracellular Ca 2+ levels. Treatments known to inhibit Ca 2+ retention by mitochondria lead to an increased transmitter liberation in the absence of external Ca 2+ , both at the frog neuromuscular junction and from isolated nerve endings. Sodium ions stimulate Ca 2+ efflux from mitochondria isolated from excitable tissues. In the present study, the effect of increasing internal Na + levels on [ 3 H]γ‐aminobutyric acid ([ 3 H]GAB a ) release from isolated nerve endings is reported. Results show that the efflux of [ 3 H]GABA from prelabeled synaptosomes is stimulated by ouabain, veratrine, gramicidin D, and K + ‐free medium, which increase the internal sodium concentration. This effect was not observed when Na + was omitted from the incubation medium and it was independent of external Ca 2+ , the experiments having been performed in a Ca 2+ ‐free, EGTA‐containing medium. Since preincubation of synaptosomes with 2,4‐diaminobutyric acid did not prevent the stimulatory effect of increased internal Na + levels on [ 3 H]GABA efflux, it appears to be unrelated to an enhanced activity of the outward carrier‐mediated GABA transport. These results suggest that the augmented release of [ 3 H]GABA may be due to an increased Ca 2+ efflux from mitochondria eiicited by the accumulation of Na + at the nerve endings. Sandoval M. E. Sodium‐dependent efflux of [ 3 H]GABA from synaptosomes probably related to mitochondrial calcium mobilization. J. Neurochem . 35 , 915–921 (1980).