MIDAZOLAM IMPROVES ELECTROPHYSIOLOGIC RECOVERY AFTER ANOXIA AND REDUCES THE CHANGES IN ATP LEVELS AND CALCIUM INFLUX DURING ANOXIA IN THE RAT HIPPOCAMPAL SLICE
MIDAZOLAM IMPROVES ELECTROPHYSIOLOGIC RECOVERY AFTER ANOXIA AND REDUCES THE CHANGES IN ATP LEVELS AND CALCIUM INFLUX DURING ANOXIA IN THE RAT HIPPOCAMPAL SLICE
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DOI：
10.1097/00000542-199106000-00021
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发表时间：
1991-06-01
期刊：
影响因子：
8.8
通讯作者：
COTTRELL, JE
中科院分区：
文献类型：
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作者：
ABRAMOWICZ, AE;KASS, IS;COTTRELL, JE
由于兴奋性传导阻滞剂已被证明可以减少缺氧和缺血性神经元损伤，因此通过咪达唑仑等药物增强抑制性传导可能具有类似的保护作用。 大鼠海马切片在体外保存并用于确定咪达唑仑是否以及通过什么机制改善缺氧后诱发反应的恢复。 切片中的 Schaffer 侧支通路受到电刺激，并从突触后的 CA1 锥体细胞记录细胞外电位（诱发的群体尖峰）。 通过用充有95％氮气-5％二氧化碳的人工脑脊液代替充有95％氧气-5％二氧化碳的液体来使切片缺氧。 恢复百分比表示为缺氧后 60 分钟诱发群体峰值的幅度除以缺氧前的幅度。 该模型中的保护被定义为与未处理切片的恢复相比，恢复百分比显着提高（P < 0.05）。 缺氧 5 分钟后 (4 +/- 2%)，CA1 锥体细胞记录的反应没有恢复（平均值 +/- 平均值的标准误差 [SEM]）。 在缺氧之前、期间和之后10分钟用咪达唑仑处理切片。 当咪达唑仑 (1-mu-M) 溶解在水 (3 +/- 3%) 或二甲亚砜 (DMSO) (1 +/- 1%) 中时，不会增强缺氧后的恢复。 当溶解在 DMSO (27 +/- 7%) 中时，较高浓度的咪达唑仑 (100-mu-M) 确实能提高回收率，但溶解在水 (5 +/- 2%) 中时则不会。 为了测试用溶解在水中的咪达唑仑长时间预处理是否会增强恢复，在缺氧之前将切片处理 30 分钟。 在这些条件下，溶解在水中的 100-mu-M 咪达唑仑显着提高了回收率 (63 +/- 13%)。 氟马西尼 (33-mu-M) 是一种中枢苯二氮卓类拮抗剂，可完全阻断咪达唑仑的这种保护作用 (5 +/- 4%)。 令人惊讶的是，高浓度的咪达唑仑 (100-mu-M) 增加了缺氧前反应的大小 (132 +/- 7%)。 这种效应不能被氟马西尼 (33-mu-M) 逆转，因此被认为不是由于中枢苯二氮卓受体的激活所致。 当沐浴介质中存在 100-mu-M 咪达唑仑时，三磷酸腺苷 (ATP) 在缺氧期间保持在显着较高的水平（1.58 +/- 0.12 与 2.02 +/- 0.13 nM/mg 干重）。 通过 Ca-45 摄取测量的净钙流入量在高浓度咪达唑仑缺氧期间减少（6.56 +/- 0.18 对比 4.9 +/- 0.13 nM/mg 干重）。 作者得出结论，在该体外模型中，高浓度的咪达唑仑可防止海马体缺氧损伤。这种保护可能是由于缺氧期间钙流入减少和咪达唑仑维持 ATP 水平所致。
Since blockers of excitatory transmission have been shown to reduce anoxic and ischemic neuronal damage, augmentation of inhibitory transmission by agents such as midazolam might have a similar protective effect. Rat hippocampal slices were maintained in vitro and used to determine whether and by what mechanism midazolam improves recovery of evoked responses after anoxia. The Schaffer collateral pathway in the slice was stimulated electrically, and an extracellular potential, the evoked population spike, was recorded from the CA1 pyramidal cells, which are postsynaptic. The slices were made anoxic by substituting artificial cerebrospinal fluid aerated with 95% nitrogen-5% carbon dioxide for fluid aerated with 95% oxygen-5% carbon dioxide. Percentage recovery was expressed as the amplitude of the evoked population spike 60 min after anoxia divided by its preanoxic amplitude. Protection in this model is defined as a significant (P < 0.05) improvement in percentage recovery compared to the recovery of untreated slices. There was no recovery of the response recorded from CA1 pyramidal cells after 5 min of anoxia (4 +/- 2%) (mean +/- standard error of the mean [SEM]). Slices were treated with midazolam 10 min before, during, and 10 min after anoxia. Midazolam (1-mu-M) did not enhance recovery after anoxia when dissolved either in water (3 +/- 3%) or in dimethyl sulfoxide (DMSO) (1 +/- 1%). A higher concentration of midazolam (100-mu-M) did enhance recovery when dissolved in DMSO (27 +/- 7%) but not when dissolved in water (5 +/- 2%). To test whether prolonged pretreatment with midazolam dissolved in water would enhance recovery, slices were treated for 30 min prior to anoxia. Under these conditions, 100-mu-M midazolam dissolved in water significantly improved recovery (63 +/- 13%). Flumazenil (33-mu-M), a central benzodiazepine antagonist, completely blocked this protective effect of midazolam (5 +/- 4%). Surprisingly, high concentrations of midazolam (100-mu-M) increased the size of the response before anoxia (132 +/- 7%). This effect was not reversed by flumazenil (33-mu-M) and therefore is believed not to be due to activation of the central benzodiazepine receptor. Adenosine triphosphate (ATP) was maintained at a significantly higher level during anoxia when 100-mu-M midazolam was present in the bathing medium (1.58 +/- 0.12 vs. 2.02 +/- 0.13 nM/mg dry weight). Net calcium influx, as measured by Ca-45 uptake, was reduced during anoxia with high concentrations of midazolam (6.56 +/- 0.18 vs. 4.9 +/- 0.13 nM/mg dry weight). The authors conclude that high concentration of midazolam protect against anoxic damage to the hippocampus in this in vitro model. This protection may be due to reduction of calcium influx and maintenance of ATP levels by midazolam during anoxia.