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Bretylium or 6‐OHDA‐resistant, action potential‐evoked Ca 2+ transients in varicosities of the mouse vas deferens
Author(s) -
Jackson V Margaret,
Cunnane Tom C
Publication year - 2002
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 - 10.1038/sj.bjp.0704677
Subject(s) - bretylium , vas deferens , calcium , contraction (grammar) , excitatory postsynaptic potential , medicine , endocrinology , chemistry , neuroeffector , muscle contraction , electrophysiology , biology , adrenergic , inhibitory postsynaptic potential , stimulation , receptor
Action potential‐evoked calcium transients in varicosities in mouse vas deferens were monitored using laser scanning confocal microscopy. Their significance was examined by comparison with excitatory junction potentials (EJPs) and neurogenic contractions, both indirect measurements of transmitter release. Bretylium abolished EJPs, as well as the ATP and NA‐mediated phases of contraction. However, bretylium revealed a prominent late component of contraction that was atropine‐sensitive. Bretylium abolished calcium transients in 21%, enhanced in 16% and had no effect in 63% of varicosities examined. Pre‐treatment with 6‐OHDA reduced NA levels to below detectable levels but many strings of varicosities still responded to nerve impulses with ‘normal’ calcium transients. Varicosities in which calcium transients were abolished by these agents were sympathetic. The identity of those varicosities in which calcium transients were resistant to bretylium (sympathetic but no uptake‐1 sites, parasympathetic, sensory) remains to be established. British Journal of Pharmacology (2002) 135 , 1845–1850; doi: 10.1038/sj.bjp.0704677