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SODIUM AND THE FLUX OF CALCIUM IONS IN ELECTRICALLY‐STIMULATED CEREBRAL TISSUE
Author(s) -
Bull R. J.,
Trevor A. J.
Publication year - 1972
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.1471-4159.1972.tb01421.x
Subject(s) - efflux , tetrodotoxin , extracellular , calcium , chemistry , stimulation , incubation , sodium , biophysics , intracellular , kinetics , neurotransmitter , endocrinology , medicine , biochemistry , biology , receptor , physics , organic chemistry , quantum mechanics
— The rate of efflux of 45 Ca 2+ from slices of rat cerebral cortex was resolved into two exponential curves which were attributed to an extracellular component and an intracellular or bound component. Electrical stimulation increased efflux of 45 Ca 2+ from the more stable pool and the time course for the redistribution of Na + and K + paralleled that for the increased efflux of Ca 2+ . This effect of stimulationwas dependent on the presence of Na + in the incubation medium. Lack of Na + in the medium during loading of the slices with 45 Ca 2+ increased uptake but on subsequent transfer to a medium containing Na + , electrical pulses failed to increase the rate of efflux of 45 Ca 2+ . In unstimulated slices, the rate of efflux of 45 Ca 2+ was dependent upon the concentration ratio of Na + to Ca 2+ in the incubation medium. Saxitoxin and tetrodotoxin inhibited the increased efflux of 45 Ca 2+ that occurred during electrical stimulation but exerted no effect on Ca 2+ ‐Ca 2+ exchange. Our results suggest that there is a Na + ‐dependent turnover of Ca 2+ in brain slices which may involve changes in affinity at a common binding site. The possible involvement of such a Na + ‐Ca 2+ interaction in the regulation of neurotransmitter function is discussed.