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Muscarinic (Mi) receptor‐mediated inhibition of K + ‐evoked [ 3 H]‐noradrenaline release from human neuroblastoma (SH‐SY5Y) cells via inhibition of L‐ and N‐type Ca 2+ channels
Author(s) -
McDonald R.L.,
Vaughan P.F.T.,
Peers C.
Publication year - 1994
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.1476-5381.1994.tb17035.x
Subject(s) - muscarine , veratridine , oxotremorine , chemistry , carbachol , muscarinic acetylcholine receptor , pirenzepine , endocrinology , channel blocker , acetylcholine , medicine , biophysics , receptor , biochemistry , sodium , sodium channel , calcium , biology , organic chemistry
1 Human neuroblastoma (SH‐SY5Y) cells were preincubated with [ 3 H]‐noradrenaline ([ 3 H]‐NA) in the presence of 0.2 m m pargyline to examine the modulation of K + ‐evoked [ 3 H]‐NA release by muscarinic agonists. 2 Release of [ 3 H]‐NA evoked by 4 min exposure to 100 m m K + could be partially inhibited by 5 μ m nifedipine and partially inhibited by 100 n m ω‐conotoxin GVIA (ω‐CgTx). When nifedipine and (ω‐CgTx were added together, evoked release was inhibited by approximately 93%. 3 K + ‐evoked [ 3 H]‐NA release was inhibited by > 90% by pretreatment of cells for 2 min with muscarine, carbachol or oxotremorine methiodide (each at 300 μ m ). For muscarine, inhibition of evoked release was both time‐ and concentration‐dependent and was reversible. Muscarine also inhibited [ 3 H]‐NA release evoked by veratridine (28 μ m ) and replacement of extracellular Ca 2+ with Ba 2+ , but not that evoked by the Ca 2+ ionophore, A23187 (19 μ m ). 4 Residual K + ‐evoked [ 3 H]‐NA release measured in the presence of either nifedipine (5 μ m ) or ω‐CgTx (100 n m ) was inhibited by muscarine with a similar potency as release evoked in the absence of either Ca 2+ channel blocker. Pretreatment of cells for 16–24 h with pertussis toxin (200 ng ml −1 ) did not affect K + ‐evoked release per se or the ability of muscarine to inhibit such release. 5 Muscarinic inhibition of K + ‐evoked [ 3 H]‐NA release was potently antagonized by pirenzepine (pA 2 8.14) and by hexahydrosiladiphenidol (pA 2 9.03), suggesting the involvement of an M 1 receptor. 6 Our results demonstrate that 100 m m K + ‐evoked release of [ 3 H]‐NA from the human neuroblastoma is mediated by activation of both L‐ and N‐type Ca 2+ channels. Activation of muscarinic M 1 receptors can inhibit release via a pertussis toxin‐insensitive mechanism which involves non‐selective inhibition of L‐ and N‐type Ca 2+ channels.