Functional rescue of N-methyl-N-nitrosourea-induced retinopathy by nicotinamide in Sprague-Dawley rats

Purpose. A single intraperitoneal injection of 60 mg/kg body weight of N-methyl-N-nitrosourea (MNU) into rats results in retinal degeneration over a 7-day period in all treated animals. The purpose of this study was to determine whether nicotinamide (NAM) can lead to a functional rescue of the MNU-induced retinopathy. Methods. NAM, a water-soluble B-group vitamin (vitamin BA was administered immediately after MNU injection, and retinas were examined morphologically and functionally. Results. Morphologically, 1000 mg/kg NAM completely suppressed and 50 mg/kg NAM partially suppressed the photoreceptor cell loss. Functionally, scotopic and photopic electroretinographic (ERG) recordings showed that both rod and cone photoreceptor cells were well protected from MNU damage by 1000 mg/kg NAM and partially protected by 50 mg/kg NAM. Conclusions. NAM can protect photoreceptor cells from MNU-induced retinopathy both structurally and functionally.