Capsaicin-induced corneal changes associated with sensory denervation in neonatal rat.

A single subcutaneous injection of capsaicin (50 mg/kg) to neonatal Wistar rats induced prominent corneal changes consisting of initial edematous lesions and late degenerative opacities in the epithelium and stroma, with disintegrated epithelial cells on histologic sections. Qualitative and quantitative analyses of the corneal nerves by means of gold chloride impregnation revealed a marked degeneration of the intraepithelial terminal fibers, resulting in a significant decrease in neural density by over 70% of the normal value at 4 and 6 weeks after neonatal capsaicin treatment. Thereafter, regeneration of nerve fibers occurred, but the neural density did not return to the normal level at 6 months after treatment.