title: Comparison of the relaxing effects of cicletanine and cromakalim on vascular smooth muscle.
abstract: Cicletanine inhibited the spontaneous activity of portal vein preparations (rat, guinea pig, and rabbit) and that produced by norepinephrine or an increase in external K+ concentration to 20 mmol/L in seven types of vascular smooth muscle preparation (portal vein of rat, guinea pig, and rabbit; aorta of rat and guinea pig; and iliac artery and ear artery of rabbit). The cicletanine EC50 was approximately 10(-4) mol/L. Contractions produced by K+ = 80 mmol/L were also inhibited by cicletanine in most preparations. Only in aortic strips of rat and guinea pig and in rabbit iliac artery were the concentration-response relationships for cicletanine shifted to the right, yielding EC50 values of approximately 3 x 10(-4) mol/L. In contrast, the inhibitory effects of the potassium channel opener cromakalim (BRL 34915) were completely abolished during K+ = 80 mmol/L treatment in all preparations. The inhibitory effect of cromakalim under the other test conditions (above) was completely antagonized by application of glibenclamide, 10(-5) mol/L, whereas this treatment had only negligible effects on cicletanine inhibition in most preparations. The results indicate that a potassium channel opening effect does not contribute significantly to the inhibitory effect of cicletanine on vascular smooth muscle.
authors.affiliation: Department of Physiology, University of Marburg, Marburg/Lahn, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Deitmer
authors.forename: K
authors.initials: K
authors.lastname: Golenhofen
authors.forename: T
authors.initials: T
authors.lastname: Noack
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001011:Aorta / Q000187:drug effects; D001578:Benzopyrans / Q000494:pharmacology*; D019806:Cromakalim; D004232:Diuretics / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D006168:Guinea Pigs; D007083:Iliac Artery / Q000187:drug effects; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D011169:Portal Vein / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D011725:Pyridines; D011758:Pyrroles / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000959:Antihypertensive Agents; D001578:Benzopyrans; D004232:Diuretics; D011725:Pyridines; D011758:Pyrroles; D014665:Vasodilator Agents; D019806:Cromakalim; C038068:cicletanine; D011188:Potassium; D005905:Glyburide; D009638:Norepinephrine