Administration of midazolam in infancy does not affect learning and memory of adult mice.

Summary 1 Midazolam is a common fast-acting GABAA receptor agonist. Recent data suggest that exposure to midazolam in early life may cause long-term effects on brain function through stable epigenetic reprogramming. The aim of the present study was to determine whether the administration of midazolam to infant mice would affect their learning and memory in adulthood. 2 An open-field test was conducted before and then 3, 24, 48 and 72 h after administration of midazolam (50 mg/kg, i.p.) to infant mice. Saline control mice received an equal volume of saline i.p. 3 h before the open-field test. Total movements, total movement time, total movement distance and velocity were analysed. Novel object recognition (NOR), Morris water-maze and passive avoidance tests were performed when the treated mice grew to adulthood (105 days of age). 3 The results of open-field test showed that midazolam significantly reduced locomotor activity (total movements, total movement time, total movement distance and velocity) in infant mice 3 and 24 h after drug administration and that these effects had disappeared by 72 h after drug administration. The results of the water-maze, NOR and passive avoidance tests in adulthood (at 105 days of age) indicated that administration of midazolam in infancy had no long-term effects on the learning and memory behaviours of adult mice compared with the saline control. 4 Acute midazolam administration to infant mice affected spontaneous locomotor activity for approximately 2 days, but did not seem to have any significant impact on cognitive functioning that lasted into adulthood.