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-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.
Bova
Sergio
S
Dipartimento di Farmacologia ed Anestesiologia, Università degli Studi di Padova, L.go E. Meneghetti 2, 35131, Padova, Italy. sergio.bova@unipd.it
Cavalli
Maurizio
M
Cima
Lorenzo
L
Luciani
Sisto
S
Saponara
Simona
S
Sgaragli
Giampietro
G
Cargnelli
Gabriella
G
Fusi
Fabio
F
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009636:Norbornanes / Q000494:pharmacology*; D051381:Rats; D011921:Rats, Inbred WKY; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D009636:Norbornanes; D014662:Vasoconstrictor Agents; C005321:norbormide