Age-related alterations of nitric oxide production in the brains of seizure-susceptible EL mice.

We evaluated age-related changes in nitric oxide (NO) production in the brains of EL mice, a strain highly susceptible to seizures. A group of EL(s) mice were tossed up weekly to induce convulsive seizures, while in a nonstimulated EL(ns) group induction of convulsive seizures was avoided. Brain levels of nitrite plus nitrate (NOx) in EL(ns) mice were significantly higher than in nonstimulated mice at 10 days, and also higher than levels at 15 and 50 weeks in either EL(s) or EL(ns) mice. A significantly higher number of NO-producing cells were demonstrated in the hippocampus and parietal cortex by staining for nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase in EL(s) mice at the ages of 15 and 50 weeks than in EL(ns) mice at the age of 6 weeks. In EL(ns) mice, significantly fewer neurons showed NADPH-diaphorase staining in the hippocampus, striatum and parietal cortex at the age of 50 weeks than at 6 weeks. The present results suggest that whole-brain NOx levels in EL(ns) and EL(s) mice and numbers of NADPH-diaphorase-positive neurons in EL(ns) mice decreased with aging, while increasing of numbers of such neurons in EL(s) mice were assumed to develop in compensation for reduction in whole-brain NOx levels.