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Nitric oxide and arachidonic acid modulation of calcium currents in postganglionic neurones of avian cultured ciliary ganglia
Author(s) -
Khurana G.,
Bennett M.R.
Publication year - 1993
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.1476-5381.1993.tb13594.x
Subject(s) - arachidonic acid , chemistry , nitric oxide , nitric oxide synthase , sodium nitroprusside , endocrinology , calcium , medicine , pharmacology , biochemistry , biology , enzyme
1 A study has been made of the modulation of high‐voltage activated transient and sustained calcium currents in cultured neurones of avian ciliary ganglia by nitric oxide (NO) and arachidonic acid. 2 Sodium nitroprusside (100 μ m ) reduced the transient calcium current ( I Ca ) on average by 31% and the sustained I Ca by 32% during a test depolarization to + 20 mV from a holding potential of −100 mV. This reduction was maintained for at least 30 min following a single application of sodium nitroprusside. 3 l ‐Arginine (270 μ m ) reduced the transient I Ca on average by 28% and the sustained I Ca by 22% and these effects were prevented by the presence of the NO‐synthase competitive blocker N G ‐nitro‐ l ‐arginine methylester ( l ‐NAME; 100 μ m ) in the bathing solution. 4 Arachidonic acid (50 μ m ) reduced the transient I Ca on average by 28% and the sustained I Ca by 33%. When added together, arachidonic acid (50 μ m ) and l ‐arginine (270 μ m ) produced the same effects as arachidonic acid alone. 5 Blocking the conversion of arachidonic acid to prostaglandins by addition of indomethacin (20 μ m ) to the bathing solution did not prevent the depression of either the transient or the sustained calcium current during application of arachidonic acid (50 μ m ). The effects of arachidonic acid were also not occluded by l ‐NAME (100 μ m ) when present in the bathing solution. 6 Inhibiting the biosynthesis of leukotrienes by applying L‐663,536 (MK‐886; 3 μ m ) to the bathing solution prevented the depression of both components of I Ca during application of arachidonic acid (50 μ m ). 7 These results indicate that endogenous NO and arachidonic acid pathways are present in parasympathetic ciliary neurones, and that both act to depress high‐voltage, gated, calcium channel activity.