Amelioration of Endothelin-1–Induced Optic Nerve Head Ischemia by Topical Bunazosin

Abstract

Purpose: To investigate the effects of bunazosin hydrochloride, an α₁-adrenergic blocker, on the impairment of optic nerve head (ONH) blood flow and depression of visual function induced by repeated intravitreal injections of endothelin-1 (ET-1) in rabbits. Method: We injected ET-1 (20 pmol) into the right posterior vitreous of rabbits twice a week for 4 weeks, and the observation period was set at 8 weeks (starting from the first injection). The animals that received ET-1 were divided into two groups: twice a day for 8 weeks, one group received topical 0.01% bunazosin, while the second received the vehicle for bunazosin. The ONH blood flow was monitored using the laser speckle method, and visual function was assessed by examining visually evoked potentials (VEPs). Changes in the ONH cup/disk area and in the number of cells in the retinal ganglion cell layer (GCL) were also determined.Results: Repeated injections of ET-1 decreased the ONH blood flow, prolonged the VEP implicit time, enlarged the optic cup, and decreased the number of GCL cells. Topical bunazosin significantly decreased these impairments. Conclusions: These results indicate that in rabbits, topical bunazosin suppresses the changes in ONH circulation and function induced by intravitreal ET-1.

Key Words:

• bunazosin;
• endothelin-1;
• optic nerve head blood flow;
• rabbit;
• visually evoked potential