Objective To observe the effect of Midazolam on caspase-3 activation of cortical neurons in rat brain.    Methods The experiment consisted of part A and part B

including 64 7-day-old Sprague Dawley rats of either sex. In part A 24 rats were randomly divided into 4 groups according to the time point when the arterial blood was collected after intraperitoneal injection of 18.0 mg/kg Midazolam(n=6 in each group)

group A1 without Midazolam treatment as control

group A2 (15 min)

group A3 (30 min)

group A4 (60 min). In part B

40 rats were randomly divided into groups B2-B5 (n=8 in each group) according to the dose of Midazolam (4.5

9.0

14.5

18.0 mg/kg) and group B1 as control receiving 18.0 mg/kg normal saline. Both control and experimental rats were perfused transcardially with paraformaldehyde 6 h after Midazolam treatment

then their brains takenout were used for caspase-3 examination by immunohistochemistry.    Results Single injection of Midazolam did not induce hypoxia/ischemia in 7-day-old SD rats

but led to the activation of caspase-3 in cerebral neurons. Furthermore

higher single dose of Midazolam enhanced the activation of caspase-3 more.    Conclusion Midazolam triggers the activation of caspase-3 in cortical neurons and may lead to neuronal apoptosis.