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Activation of nicotinic acetylcholine receptors expressed in quail fibroblasts: effects on intracellular calcium
Author(s) -
Cross M.L.,
Jane S.D.,
Wild A.E.,
Foreman R.C.,
Chad J.E.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb15934.x
Subject(s) - nicotinic agonist , calcium , biophysics , chemistry , acetylcholine , extracellular , voltage dependent calcium channel , quail , agonist , depolarization , nifedipine , calcium in biology , endocrinology , receptor , acetylcholine receptor , alpha 4 beta 2 nicotinic receptor , intracellular , medicine , nicotinic acetylcholine receptor , biology , biochemistry , organic chemistry
1 The aim of these experiments was to determine the ability of the muscle‐type nicotinic acetylcholine receptor (AChR) stably expressed in quail fibroblasts (QF18 cells) to elevate intracellular calcium ([Ca 2+ ] i ) upon activation. Ratiometric confocal microscopy, with the calcium‐sensitive fluorescent dye Indo‐1 was used. 2 Application of the nicotinic agonist, suberyldicholine (SDC), to the transfected QF18 cells caused an increase in [Ca 2+ ] i . Control [Ca 2+ ] i levels in QF18 cells were found to be 164 ± 22 nM (mean ± s.e.mean; n = 40 cells) rising to 600 ± 81 nM on addition of SDC (10 μ m ; n =15 cells), whereas no increase in [Ca 2+ ] i was seen in non‐transfected control QT6 fibroblasts (before: 128 ± 9 nM, n = 40; after: 113±13 nM, n = 15). 3 The increase in [Ca 2+ ] i caused by application of SDC was dose‐dependent, with an EC 50 value of 12.7 ± 5.9 μm ( n =14). 4 The responses to SDC in QF18 cells were blocked by prior application of α‐bungarotoxin (200 nM), by the addition of Ca 2+ (100 μ m ), by removal of Na + ions from the extracellular solution, or by the voltage‐sensitive calcium channel blockers nifedipine and ω‐conotoxin, which act with IC 50 values of 100 nM and 100 pM respectively. 5 We conclude that activation of the nicotinic AChRs leads to a Na + ‐dependent depolarization and hence activation of endogenous voltage‐sensitive Ca 2+ channels in the plasma membrane and an increase in [Ca 2+ ] i . There is no significant entry of Ca 2+ through the nicotinic receptor itself.