| Purpose and meaning:The ability of learning and memory, not only is one of the most basic ability that in the human activity such as work and life, but also ensure that the most important animals to survive in the nature. The ERK/CREB pathway and Arc gene play a huge role in learning and memory cognitive process. Midazolam could adversely affect learning and memory ability, but the possible mechanism is not clear. Thus, in this study we investigated the effects of midazolam exposure on learning and memory ability of rats in the Morris water maze test, and PKA/ERK/CREB pathway and Arc gene expression in the hippocampus of rats. According to the theory for the mechanism of learning and memory and the pharmacological characteristics of midazolam, further explore the effect of midazolam on learning and memory ability of rats and its possible mechanism. Provide a certain amount of laboratory research evidence for the mechanism of midazolam caused cognitive dysfunction.Methods:72 male wistar rats, first randomly selected 24 rats were divided into four groups of water maze experiment was carried out: Midazolam high dose group(m H group, 150mg/kg), Midazolam middle dose group(mM group, 60mg/kg), Midazolam low dose group( mL group, 20mg/kg) and normal saline group(mNS). Clear immediately after the treatment by water maze of sea trial, at the same time every day, training after being given midazolam rats can exercise spontaneously, for 5 consecutive days, on the sixth day, at the same time, the drug again, conscious immediate spatial probe test of rats experiment was carried out. The remaining 48 rats were randomly divided into four groups, 12 per group: Midazolam high dose group(MH group, 150mg/kg), Midazolam middle dose group(MM group, 60mg/kg), Midazolam low dose group(ML group, 20mg/kg) and normal saline group(MNS). Each dose group was divided into four subgroups, dosage groups of rats respectively after dosing mild sedation or positive reflection disappeared(T1), 10 min after severe sedation or over are reflected or 25 min(T2), awakening(T3) and 24 h after dosing(T4) beheaded kill rats, normal saline group rats respectively 5 min after intraperitoneal injection of saline solution(T1), 30 min time(T2), 1 h(T3) a nd 24 h(T4) beheaded executed, separation of hippocampus, detected using RT-PCR method PKA, ERK1, ERK2, after CREB and Arc m RNA expression, using Western Blot method to detect the p-ERK1/2 and p-after CREB protein expression.Results:(1) The ability of learning and memory in rats in water maze test experiment, compared with normal saline group, midazolam group rats average escape latency period extend in the navigation test, cross platform in space exploration test times and the third quadrant residence time ratio decreases, and the greater the midazolam dosage, the longer the average escape latency of rats, through the platform number and the third quadrant time rates are lower.(2) RT-PCR and Western Blot method to detect the rat hippocampus of PKA, ERK1, ERK2, CREB, Arc m RNA expression and p-ERK1/2, p-CREB protein expression, according to the results of midazolam dosage dependent on type of inhibiting the PKA, ERK1, ERK2, CREB, Arc mRNA expression and p-ERK1/2, p-CREB protein expression, but the inhibition in 24 h after dosing disappeared, PKA in hippocampus of rats, ERK1, ERK2, after CREB, Arc mRNA expression and p-ERK1/2, p-CREB protein expression level back to the control group.Conclusion: We according to the above test results, sedative dose and anes thetic doses of midazolam can damage rat spatial learning and memory ability, and the higher the midazolam dosage, the greater the damage of rats learning and memory abilities. Midazolam in dose dependent type inhibits hippocampal PKA-ERK-CREB signaling pathways and the expression of the Arc. So we speculate that in the hippocampus of rats PKA-ERK-CREB signaling pathway and Arc gene expression is restrained by midazolam may be lead to damage one of the mechanisms of learning and memory in rat. |
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