A New Calcium Channel Antagonist, Lomerizine, Alleviates Secondary Retinal Ganglion Cell Death After Optic Nerve Injury in the Rat

Abstract

Purpose: We investigated whether lomerizine, a new diphenylmethylpiperazine calcium channel blocker, exerted a neuroprotective effect on axonal or retinal damage induced by optic nerve injury in the rat. Methods: A partial crush lesion was inflicted unilaterally on the optic nerve, 2 mm behind the globe, in adult Wistar albino rats. Animals were treated with the vehicle, 10 or 30 mg/kg lomerizine. Each solution was given orally twice daily for 4 weeks. One week before euthanization, Fluoro-Gold (FG) was injected into both superior colliculi to retrogradely label surviving retinal ganglion cells (RGCs). Approximately 1 month after the optic nerve injury, the retinal damage was assessed morphologically, and the optic nerve axons surrounding the initial lesion were examined histologically. Results: The mean RGC density in the control group decreased to 65.9 ± 1.32% of the contralateral eye, whereas the systemic application of 10 or 30 mg/kg of lomerizine significantly enhanced the RGC survival to 88.1 ± 0.38% and 89.8 ± 0.28%, respectively. Histological examination of damaged axons revealed no significant enhancement of the density or total number of axons of the retinal ganglion cells in the lomerizine-treated group. The crush force we employed caused no significant morphological differences in the retinal layers between the sham-operated animals and the animals from the experimental groups. Conclusions: Our findings suggest that lomerizine alleviates secondary degeneration of RGCs induced by an optic nerve crush injury in the rat, presumably by improving the impaired axoplasmic flow.