Effects of β antagonists on mechanical properties in rabbit ciliary artery

Abstract

Betaxolol and timolol could directly relax rabbit ciliary artery in vitro at relatively high concentrations, and relaxation was not due to NO released from the preparation. Presumably, this relaxation occurs through action similar to Ca antagonists. However, the clinical importance of this effect is not yet clear. Carteolol had no relaxant effect in vitro.

Effect and Mechanism of Betaxolol and Timolol on Vascular Relaxation in Isolated Rabbit Ciliary Artery

“…The relaxation induced by betaxolol was not affected by L-NAME or by mechanical endothelium denudation. These results were very similar to those of our previous data, reported by Morimoto et al 6 However, the precise mechanism of the relaxation induced by betaxolol was not clear.…”

“…6,[11][12][13][14] The rabbit ciliary artery is innervated by at least two types of nerves: adrenergic nerves, which evoke contraction, and nerve fi bers that cause an endothelium-independent release of nitric oxide (NO). Pilocarpine relaxation of this muscle is dependent on the endothelium and NO synthesis.…”

“…5 We have previously reported that betaxolol and timolol could directly relax rabbit ciliary artery in vitro at relatively high concentrations, and the relaxing action with betaxolol was more potent than that with timolol at equal concentrations. 6 Although the pattern of relaxation induced by the β 1 -adrenergic antagonists was similar to that of calciumchannel blockers, the exact mechanism of this relaxation was not clear. Recently, fl uorescent dyes have become available for measuring the change in cytosolic Ca 2+ concentrations in various biological preparations.…”

Pharmacological effects of latanoprost, prostaglandin E2, and F2 α on isolated rabbit ciliary artery

“…Of all the glaucoma drugs we have so far tested, latanoprost exerted the most potent relaxing effect on this artery [9,10]. This relaxation did not depend on endothelium and was not caused by intrinsic PG, CGRP, or NO.…”

Vasodilatory Effects of Nipradilol, an α- and β-adrenergic Blocker with Nitric Oxide Releasing Action, in Rabbit Ciliary Artery

“…We have reported that timolol, betaxolol (Hayashi-Morimoto et al, 1999), pilocarpine (Yoshitomi et al, 2000), and unoprostone isopropyl (Hayashi et al, 2000) induced relaxation of the isolated rabbit ciliary artery, each acting through different mechanisms. Kanno et al (1998) using laser speckle methods in rabbits, reported that topical application of 0 .…”