[Evaluation of bunazosin hydrochloride with a model of ocular circulation disturbance induced by endothelin-1].

We studied the effect of bunazosin hydrochloride, a selective alpha-1 blocker under development as an antiglaucomatous drug, on the circulation of the optic nerve head (ONH) in normal and endothelin-1 treated albino rabbit eyes. The effect was investigated by measurement of the capillary blood flow in the ONH, using a hydrogen gas clearance flowmeter (for 5 hours). The relative caliber of the retinal artery (the caliber of the retinal artery at the edge of the ONH/that of the ONH) was also measured, using fundus photography. Administration of bunazosin hydrochloride had no significant effect on the capillary blood flow in the ONH in normal eyes, but it inhibited the decrease of blood flow for at least 5 hours in the endothelin-1 treated eyes. The relative caliber of the retinal artery decreased in the endothelin-1 treated eyes (maximum at 5 hours), but previous administration of bunazosin hydrochloride inhibited the decrease. Thus, Bunazosin hydrochloride inhibits the disturbance of ONH circulation induced by endothelin-1 and promises to be useful also with regard to the ocular circulation.