Nicardipine modification of endothelin-1 effects on visual evoked potential.
Endothelin-1 (ET-1), a vascular endothelium-derived peptide, regulates microcirculation by modulating Ca2+ ion channels. Intravitreally injected ET-1 constricts retinal vessels and reduces blood flow in the optic nerve capillaries. We examined the antagonistic effect of a calcium-ion channel blocker, nicardipine, on ET-1 effects on visual evoked potential (VEP). ET-1 (10(-6); 10 microL) was injected into the posterior vitreous of rabbit eyes. Intravenous nicardipine (20 micrograms/kg) was also given, and VEP was monitored for 2 hours following injection. Thirty minutes after injection, ET-1 had reduced VEP amplitude to 42.6% of the baseline level. The reduction effect continued for the remainder of the study. Nicardipine suppressed the ET-1-induced reduction of VEP amplitude (P < 0.05, Scheffe). The vasospasm produced by ET-1, which reduces the VEP amplitude, involves the CA2+ ion channel. Since nicardipine interferes with the activity of ET-1, we believe that Ca2+ channel blockers can be useful in the treatment of ischemic retinal and optic nerve disorders that are related to abnormal ET-1 production.
Ota
M
M
Department of Ophthalmology, Osaka Medical College, Japan.
Oku
H
H
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000494:pharmacology*; D019332:Endothelin-1 / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D005074:Evoked Potentials, Visual / Q000187:drug effects* / Q000502:physiology; D007262:Infusions, Intravenous; D007267:Injections; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009529:Nicardipine / Q000008:administration & dosage / Q000494:pharmacology*; D009900:Optic Nerve / Q000098:blood supply / Q000502:physiology; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000502:physiology; D012171:Retinal Vessels / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects; D014795:Visual Pathways / Q000187:drug effects* / Q000502:physiology; D014822:Vitreous Body
D002121:Calcium Channel Blockers; D019332:Endothelin-1; D009529:Nicardipine