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ON THE CONDUCTANCE PATHWAY TRAVERSED BY STRONTIUM IN MEDIATING THE ASYNCHRONOUS RELEASE OF ACETYLCHOLINE BY MOTOR NERVE IMPULSES
Author(s) -
MELLOW A.M.,
PHILLIPS T.E.,
SILINSKY E.M.
Publication year - 1978
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.1476-5381.1978.tb09750.x
Subject(s) - acetylcholine , strontium , motor nerve , neuroscience , neuromuscular junction , chemistry , conductance , biophysics , biology , endocrinology , physics , organic chemistry , condensed matter physics
A study was made to determine whether the Sr 2+ ‐dependent asynchronous release of acetylcholine by nerve impulses is mediated by the conventional Ca 2+ conductance channel or, as has been suggested recently, through an alternative ion pathway. Experiments were performed on the frog neuromuscular junction by the use of standard electrophysiological techniques. Repetitive nerve stimulation in Sr 2+ ‐Ringer solutions caused a marked increase in miniature end‐plate potential (m.e.p.p.) frequency which was dependent on Sr 2+ concentration and inhibited in a competitive fashion by the known Ca 2+ antagonists, Co 2 + and Mg 2 + . The equilibrium dissociation constants (K d s) determined for both Co 2+ (0.09 + 0.01 m m , mean ± s.e. mean, n = 5) and Mg 2+ (3.7 ± 0.3 m m , mean ± s.e. mean, n = 4) were essentially the same as the reported values for these antagonists in blocking Ca 2+ ‐mediated transmitter release by nerve impulses. These results suggest that Sr 2+ mediates asynchronous evoked transmitter release through the conventional calcium conductance channel.