Relaxant and Ca2+ channel blocking properties of norbormide on rat non-vascular smooth muscles

We have investigated the effects of the rat-specific vasoconstrictor agent norbormide on the mechanical and electrophysiological properties of rat non-vascular smooth muscles. Norbormide (50 microM) did not affect the resting tone of urinary bladder, tracheal, and duodenal rings. In all tissues, KCl...

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Published in:European journal of pharmacology 2003-06, Vol.470 (3), p.185-191
Main Authors: BOVA, Sergio, CAVALLI, Maurizio, CIMA, Lorenzo, LUCIANI, Sisto, SAPONARA, Simona, SGARAGLI, Giampietro, CARGNELLI, Gabriella, FUSI, Fabio
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Calcium Channel Blockers - pharmacology
Dose-Response Relationship, Drug
In Vitro Techniques
Male
Medical sciences
Muscle Relaxation - drug effects
Muscle Relaxation - physiology
Muscle, Smooth - drug effects
Muscle, Smooth - physiology
Norbornanes - pharmacology
Rats
Rats, Inbred WKY
Vasoconstrictor Agents - pharmacology
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Summary:We have investigated the effects of the rat-specific vasoconstrictor agent norbormide on the mechanical and electrophysiological properties of rat non-vascular smooth muscles. Norbormide (50 microM) did not affect the resting tone of urinary bladder, tracheal, and duodenal rings. In all tissues, KCl-induced concentration-response curves were shifted downward by norbormide (5 and 50 microM). In urinary bladder and tracheal rings, norbormide inhibited contractile responses to carbachol only at the higher concentration (50 microM). In single gastric fundus myocytes, 50 microM norbormide inhibited L-type Ca(2+) current (I(Ca(L))) by about 60%, neither affecting both activation and inactivation rates of the current nor the current-voltage curve along the voltage axis. Our results indicate that rat non-vascular smooth muscles are relaxed by norbormide with a mechanism likely involving a reduction of Ca(2+) entry through L-type Ca(2+) channels.
ISSN:0014-2999
1879-0712
DOI:10.1016/S0014-2999(03)01797-7