Rats poisoned with sarin enter into ahyper-cholinergic crisis characterized by excessive salivation, respiratory distress, tremors, seizures, and death. Through the use of rescue medications and an anticonvulsant, death can be avoided in many animals, with the long-term consequences of poisoning partly ameliorated, especially when countermeasures are made available immediately after exposure. However, when anticonvulsant measures are delayed by as little as 30 min, clinical, neurological, cognitive, and psychiatric abnormalities may persist long after the initial exposure. This study sought to determine if the addition of the NMDA receptor antagonist Ketamine to human standard-of-care countermeasures consisting of two rescue medications (2-PAM and atropine) and an anti-convulsant (Midazolam), would afford protection against persistent neurobiological compromise. Rats were exposed to sarin (105 μg/kg via subcutaneous injection), and treated 1 min later with 2-PAM and Atropine Methyl Nitrate (IM) to minimize mortality. One of four anti-convulsant protocols was then initiated at 50 min postsarin:Midazolam alone (MDZ, a single injection (IM) at 0.66 mg/kg); Ketamine alone (KET, a series of five injections (IM) of Ketamine at 7.5 mg/kg, 90 min apart); Midazolam + low dose Ketamine (MDZ + lowKET, a single injection of Midazolam (IM) at 0.66 mg/kg, plus five sequential doses of ketamine (IM) at 2.5 mg/kg, starting at the time of Midazolam dosing and then 90 min apart); Midazolam + high dose Ketamine (MDZ + highKET, a single injection of Midazolam (IM) at 0.66 mg/kg, plus five sequential injections of 7.5 mg/kg Ketamine (IM), starting at the time of Midazolam dosing and then 90 min apart). Animals were preassigned to groups culled at post-exposure Days 1, 7 or 30, for histopathology. For all surviving animals, EEG activity was monitored through skull electrodes for 24-h beginning immediately after sarin exposure. Surviving animals also underwent 24-h EEG monitoring on Days 6, 13, and/or 29, post-sarin. Memory assessment using the Morris Water Maze was performed on Days 1, 4, 7, 14 and 30. Following sarin exposure, 85% of surviving animals demonstrated status epilepticus within 20 min. Each of the anti-convulsant protocols was sufficient to stop convulsions within 1 h of anti-convulsant administration, but all of the animals still showed signs of electrographic status for an additional 2–12 h, without substantial differentiation between treatment groups. However, for post-sarin hours 13–24, the MDZ + highKET group showed significantly less severe EEG abnormalities than the MDZ and KET groups (Mood’s Median Test, p < 0.005). At one month post-exposure, 90% of animals that had received Midazolam alone still showed evidence of some epileptiform activity. In contrast, 90% of animals that had received Midazolam + high dose Ketamine combination therapy had EEG profiles that were within normal limits. This difference in EEG outcomes was highly significant (Mood’s Median Test, p < 0.001). Likewise, on the water maze, the majority of animals that had received Midazolam combined with either high or low dose Ketamine therapy returned to near baseline levels of mnemonic performance within 2 weeks, whereas the majority of the animals that had received midazolam alone or ketamine alone demonstrated persistent and significant memory impairments even at one month postexposure (Mood’s Median Test, p < 0.005). With respect to neuronal necrosis, animals in the MDZ + highKET group showed significantly less overall damage than animals in other treatment groups (Mood’s Median Test, p < 0.001). Of special note were findings in the hippocampus, where only 12% of animals in the MDZ + highKET group showed evidence of necrosis on H&E staining, whereas 100% of animals in the KET group, 70% of animals in the MDZ group, and 40% of animals in the MDZ + lowKET group showed evidence of hippocampal necrosis. Overall, the data demonstrate that Ketamine augmentation of an atropine, 2PAM, and Midazolam standard-ofcare for sarin exposure provides clinically-relevant additional protection against the negative neurobiological consequences of sarin, even when initiation of the anti-convulsant countermeasures is delayed by 50 min.

被沙林毒中毒的大鼠进入高胆碱能危机，其特征是流涎过多，呼吸窘迫，震颤，癫痫发作和死亡。通过使用急救药物和抗惊厥药，可以避免许多动物死亡，中毒的长期后果得到部分缓解，尤其是在接触后立即采取对策的情况下。但是，如果将抗惊厥措施延迟30分钟之久，则在初次接触后很长一段时间内，临床，神经，认知和精神病学异常可能会持续存在。这项研究试图确定是否将NMDA受体拮抗剂氯胺酮添加到由两种急救药物（2-PAM和阿托品）和抗惊厥药（咪达唑仑）组成的人类护理标准对策中，将提供保护以防止持续的神经生物学损害。使大鼠暴露于沙林蛋白（通过皮下注射105μg/ kg），并在1分钟后用2-PAM和阿托品硝酸甲酯（IM）处理，以使死亡率最小化。然后在50分钟后（仅注射后剂量：Midazolam）（MDZ，单次注射（IM），剂量为0.66 mg / kg）启动四种抗惊厥方案之一。单独使用氯胺酮（KET，以7.5 mg / kg的间隔注射90分钟，进行一系列的氯胺酮五次注射（IM））；咪达唑仑+低剂量氯胺酮（MDZ + lowKET，咪达唑仑（IMZ）的单次注射剂量为0.66 mg / kg，加上五次连续剂量的氯胺酮（IM）的剂量为2.5 mg / kg，从咪达唑仑给药时开始，然后90分钟分开）; 咪达唑仑+高剂量氯胺酮（MDZ + highKET，单次注射咪达唑仑（IM）的剂量为0.66 mg / kg，再依次注射五次，每次剂量为7.5 mg / kg氯胺酮（IM），从咪达唑仑给药时开始，然后相隔90分钟）。将动物预先分配到暴露后第1、7或30天进行分类的组进行组织病理学检查。对于所有存活的动物，沙林暴露后立即开始通过头骨电极监测EEG活性24小时。存活的动物在沙林后第6、13和/或29天也接受了24小时的脑电图监测。在第1、4、7、14和30天使用莫里斯水迷宫进行记忆评估。暴露于沙林后，幸存的动物中有85％在20分钟内表现出癫痫持续状态。每种抗惊厥方案足以在抗惊厥给药后1小时内停止惊厥，但是所有动物在另外2–12 h内仍显示出电子状态的迹象，各治疗组之间没有实质性区别。然而，沙林后13-24小时，MDZ + highKET组的严重脑电图异常显着低于MDZ和KET组（情绪中位数检验，p <0.005）。暴露后一个月，仅接受咪达唑仑的动物中有90％仍显示出某些癫痫样活动的证据。相反，接受咪达唑仑+高剂量氯胺酮联合治疗的动物中有90％的脑电图处于正常范围内。脑电图结果的差异非常显着（情绪中位数检验，p <0.001）。同样，在水迷宫上，大多数接受咪达唑仑并用高剂量或低剂量氯胺酮治疗的动物在2周内恢复了接近基线的记忆功能。而大多数仅接受咪达唑仑或单独氯胺酮治疗的动物，即使在暴露后一个月，也表现出持续且显着的记忆障碍（Mood's中值检验，p <0.005）。在神经元坏死方面，MDZ + highKET组的动物表现出的总体损害显着低于其他治疗组的动物（Mood's中间值检验，p <0.001）。特别值得注意的是在海马中发现的疾病，MDZ + highKET组中只有12％的动物表现出H＆E染色坏死的证据，而KET组中的动物有100％，MDZ组的动物有70％，而40只动物MDZ + lowKET组中的动物百分比显示出海马坏死的迹象。总体而言，数据表明氯胺酮可增加阿托品2PAM的含量，