A new calcium channel antagonist, lomerizine, alleviates secondary retinal ganglion cell death after optic nerve injury in the rat.

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.