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The Effect of Barium on [ 3 H]Noradrenalin Release from the Human Neuroblastoma SH‐SY5Y
Author(s) -
Vaughan Peter F. T.,
Kaye David F.,
Ball Stephen G.,
Reeve Helen L.,
Peers Chris
Publication year - 1995
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1995.tb01074.x
Subject(s) - carbachol , sh sy5y , tetrodotoxin , chemistry , biophysics , depolarization , endocrinology , medicine , patch clamp , cell culture , neuroblastoma , biology , biochemistry , receptor , genetics
Replacement of Ca 2+ with Ba 2+ in HEPES‐buffered saline stimulated [ 3 H]noradrenalin release in the human neuroblastoma clone SH‐SY5Y by up to 20% of the cell content in the absence of other secretory stimuli. The Ba 2+ ‐evoked release was inhibited by 85% by 3 μM tetrodotoxin and 95% by 5 μM nifedipine. Ba 2+ also increased the potency of K + ‐evoked release of [ 3 H]noradrenalin, as maximal release was observed with 60 mM K + compared with the 100 mM K + necessary to achieve maximal release in the presence of Ca 2+ . In contrast, replacing Ca 2+ with Ba 2+ had little effect on carbachol‐ and bradykinin‐evoked release of [ 3 H]noradrenalin. No evidence was obtained from studies on changes in [Ca 2+ ] i (in response to 100 pM carbachol) using fura‐2 that Ba 2+ could enter intracellular stores in SH‐SY5Y cells. Whole‐cell patch‐clamp studies showed that Ba 2+ depolarizes SH‐SY5Y cells as well as enhancing inward Ca 2+ channel currents and shifting their voltage dependence to more negative values. These results are discussed in terms of the hypothesis that Ba 2+ blocks K + channels, leading to depolarization followed by opening of voltage‐sensitive Na + channels. This in turn opens voltage‐sensitive L‐type Ca 2+ channels, which are coupled to the release of [ 3 H]noradrenalin in SH‐SY5Y cells.