Authors: Yaru Dong Hitoshi Ishikawa Yazhen Wu Kimiya Shimizu Toshiaki Goseki Takeshi Yoshitomi
Publish Date: 2006/11/01
Volume: 50, Issue: 6, Pages: 504-508
Abstract
Rabbit ciliary artery specimens were mounted in a double myograph system and betaxolol timolol or another agent was introduced into the organ chamber The mechanical response of the arteries was studied using an isometric tension recording method The intracellular free calcium concentration Ca2+i was also measured using fluorescence photometryBetaxolol and timolol induced dosedependent relaxation in the rabbit ciliary arteries precontracted by highK+ Krebs solution The minimum concentrations required to cause relaxation were 10 µM of betaxolol and 30 µM of timolol At the maximum concentration of 1 mM betaxolol induced almost complete relaxation of the ciliary arteries whereas timolol induced approximately 70 relaxation These actions were not inhibited by pretreatment with 100 µM NGnitrolarginine methylester LNAME a nitric oxide synthase inhibitor or by denudation of the vascular endothelium However 300 µM of betaxolol or timolol decreased the Ca2+i of the vascular smooth muscle an action similar to that of diltiazem a typical Ltype voltage calciumchannel blockerBetaxolol a selective β1adrenoceptor antagonist and timolol a nonselective βadrenoceptor antagonist both frequently used in the medical management of glaucoma decrease Ca2+i by acting as Ca2+ channel blockers thus causing relaxation of isolated rabbit ciliary artery
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