Improving effects of topical administration of iganidipine, a new calcium channel blocker, on the impaired visual evoked potential after endothelin-1 injection into the vitreous body of rabbits

Abstract

To investigate the effect of topical iganidipine, a new dihydropyridine derivative calcium channel blocker, on impairment of the ocular circulation caused by endothelin-1 (ET-1), we examined modification of the effect of ET-1 on visual-evoked potential (VEP) in albino rabbits. To clarify whether VEP could be used to indicate the extent of ocular circulatory impairment, we evaluated the dose dependency of changes in VEP over 2 hours after intravitreal injection of 3 ET-1 doses (1.0, 3.3, or 10 pmol) and the vehicle. Then modification of the effect of ET-1 on the VEP by iganidipine was examined. One hour after the topical instillation of 0.1% iganidipine (20 microl) or its vehicle, 10 pmol of ET-1 was injected into the vitreous in rabbits. The VEP was measured for 2 hours after ET-1 application, and the response was compared between the eyes with iganidipine and vehicle pretreatment. Intravitreal injection of ET-1 dose-dependently reduced the VEP amplitude. Topical administration of 0.1% iganidipine significantly suppressed the reduction of VEP amplitude for the entire 2-hour monitoring period after intravitreal injection of 10 pmol ET-1. There was no significant change of the systemic blood pressure as well as intraocular pressure after topical administration of iganidipine. Iganidipine eyedrops may be useful for the treatment of ischemic retinal and optic nerve disorders related to abnormal ET-1 production for the maintenance of visual function.