Changes in NADPH-diaphorase positivity induced by status epilepticus in allocortical structures of the immature rat brain

The distribution and time course of changes of nicotinamide adenine dinucle otide phosphate diaphorase (NADPH-d) positivity were studied in immature ra ts (12 and 25 days old) surviving motor status epilepticus (SE) induced by a high dose of pilocarpine. Motor SE characterized by continuous convulsion s was interrupted after 2 h by an injection of clonazepam (0.5 mg/kg or 1 m g/kg in 12- and 25-day-old rats, respectively) in order to reduce mortality . Correlation between electroencephalographic and behavioral seizure activi ty was confirmed using animals with electrodes implanted bilaterally in the hippocampus and sensorimotor cortex. Brains were examined 2, 6, 13, and 21 days after motor SE using NADPH-diaphorase histochemistry, Two types of ch anges were found in both age groups: (a) decrease of NADPH-d positivity occ urred in both neuropil and cell bodies in piriform, periamygdalar, and ento rhinal cortices; and (b) NADPH-d positivity was induced in the cell bodies in the hippocampal fields CA1/2, CA3, and dentate gyrus, These changes were more intense in animals surviving SE at postnatal day 25 than in younger a ge group, and they peaked 2 days after SE. The changes observed after SE di sappeared quickly in 12-day-old rat pups, where only moderate changes could be observed in piriform, periamygdalar, and entorhinal cortices 6 days aft er SE, whereas the changes in the histochemical positivity persisted in old er animals even 21 days after SE. (C) 1999 Elsevier Science Inc.