Bretylium or 6‐OHDA‐resistant, action potential‐evoked Ca2+ transients in varicosities of the mouse vas deferens

• Published in: British journal of pharmacology Vol. 135; no. 8; pp. 1845 - 1850
• Main Authors: Jackson, V Margaret, Cunnane, Tom C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-04-2002; Nature Publishing
• Subjects: 6‐OHDA; Action Potentials - drug effects; Action Potentials - physiology; Adrenergic Agents - pharmacology; Adrenergic Fibers - drug effects; Adrenergic Fibers - physiology; Animals; Anti-Arrhythmia Agents - pharmacology; Biological and medical sciences; bretylium; Bretylium Compounds - pharmacology; Calcium - physiology; calcium imaging; Drug Resistance - physiology; Fundamental and applied biological sciences. Psychology; Male; Mice; Mice, Inbred BALB C; mouse vas deferens; Oxidopamine - pharmacology; parasympathetic; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; sensory; Special Report; Sympathetic; uptake‐1; Vas Deferens - drug effects; Vas Deferens - innervation; Vas Deferens - physiology; Vertebrates: nervous system and sense organs; Calcium; Rodentia; Electrophysiology; Action potential; Ionic current; Antiarrhythmic agent; Catecholamine; Sympathetic nervous system; In vitro; Vas deferens; Quaternary ammonium compound; Electrodiagnosis; Vertebrata; Mammalia; Mouse; Autonomic nervous system; Bretylium tosilate; Animal; Neurotransmitter; Norepinephrine; Excitatory postsynaptic potential; ATP; Urogenital system; Parasympathetic nervous system
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704677

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