[Effects of the chronic administration of midazolam on the rat hippocampus]

The effects of midazolam (MDZ) treatment during 120 days have been studied in 2 groups of young and old Wistar rats: (50 animals two months, 50 aged 24 months). 20 rats of both groups got 1 mg/kg of MDZ daily, 20 3 mg/kg, and finally 10, animals 1 ml saline all administered by gastric intubation. The general effects of MDZ (mortality, weight changes and memory of an aversive stimuli showed no significant differences with the controls either in young or old rats. In the hippocampus, the total count of neurons gave no significant differences compared to controls. However, in the group of old rats a higher number of dark and pycnotic cells, principally in those rats treated with 3 mg/kg of MDZ was observed. The global area of the CA1, CA4 fields and of the GD was significant reduced in comparison with the controls. These results favour the conclusion that the MDZ has a minimal neurotoxicity: only the group of old rats treated with 3 mg/kg showed weak signs of hippocampal effects.