[Effects of intravitreal injection of endothelin on the visual system]

Endothelin, a novel, potent, and long-acting vasoconstrictor peptide, is thought to regulate retinal circulation and its autoregulation. A disturbance in the regulation of endothelin production might contribute to the pathogenesis of retinochoroidal or optic nerve diseases. We examined the effects of endothelin on the retina and the optic nerve using the electroretinogram (ERG) and visual evoked potential (VEP). Six male albino rabbits underwent intravitreal injection of 0.1 ml (10(-5) mol/l) endothelin-1 in the right eye. Six other male albino rabbits, which were injected intravitreally with 0.1 ml of Opeguard-MA in the right eye, were used as controls. Endothelin-1 caused marked constriction of retinal vessels and pallor of the optic nerve head. These findings persisted for 10 days after endothelin-1 injection. The amplitude of the b-wave and the latency of the oscillatory potential in the ERG were not significantly different from those in controls. On the other hand, prolongation of the VEP-N1 latency was observed for 14 days after the injection. These results indicate that endothelin acts on the circulation of the optic nerve head rather than that of the retina, and that effects persist for a relatively long period.