Previous studies have shown that low doses of ketamine, an N-methyl-D-aspartate receptor antagonist, produce aberrantly strong internal representations of associatively activated but absent stimuli in humans and nonhuman animals, suggesting the validity of ketamine treatment as a preclinical model of the positive symptoms of schizophrenia, including hallucinations and delusions. However, whether acute ketamine treatment also impairs the ability to ignore present but informationally redundant stimuli, which is another hallmark of schizophrenia, remains unclear. Accordingly, the present study investigated whether injections of low-dose ketamine attenuate Kamin blocking in an appetitive conditioning preparation in mice. Mice in the blocking group were initially trained with A+ conditioning (i.e., conditioned stimulus A paired with a sucrose solution), followed by compound AX+ training, before the conditioned responses to the cue X were tested in extinction. The animals in the control group received B+ training before the AX+ training. Half of the mice in each group received an injection of 16 mg/kg ketamine before each compound conditioning session and the extinction test, whereas the other half received saline. The results showed a reliable blocking effect in the saline-treated mice, whereas the blocking effect was absent in the ketamine-treated mice. Specifically, the absence of blocking was due to the ketamine-treated mice learning about the blocked cues. This finding further validates the use of low-dose ketamine as a preclinical model of schizophrenia. It also suggests a possible link between hallucination-like aberrant processing of absent events and a reduced ability to suppress attentional processing of task-irrelevant stimuli. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

中文翻译：

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小鼠中低剂量氯胺酮会破坏卡明阻断：对精神分裂症异常刺激处理的进一步影响。

先前的研究表明，低剂量的氯胺酮（一种 N-甲基-D-天冬氨酸受体拮抗剂）会在人类和非人类动物中产生异常强烈的关联激活但不存在的刺激的内部表征，这表明氯胺酮治疗作为临床前模型的有效性。精神分裂症的阳性症状，包括幻觉和妄想。然而，急性氯胺酮治疗是否也会损害忽视现有但信息冗余刺激的能力（这是精神分裂症的另一个标志）仍不清楚。因此，本研究调查了注射低剂量氯胺酮是否会减弱小鼠食欲调节制剂中的 Kamin 阻断。阻断组中的小鼠最初接受A+条件训练（即条件刺激A与蔗糖溶液配对），然后进行复合AX+训练，然后测试对提示X的条件反应的消退。对照组的动物在AX+训练之前接受B+训练。每组中的一半小鼠在每次复合调理和消退测试前注射 16 mg/kg 氯胺酮，而另一半小鼠则注射生理盐水。结果显示，盐水处理的小鼠具有可靠的阻断作用，而氯胺酮处理的小鼠则没有阻断作用。具体来说，阻断的缺失是由于氯胺酮治疗的小鼠了解了被阻断的线索。这一发现进一步验证了低剂量氯胺酮作为精神分裂症临床前模型的用途。它还表明，对缺席事件的类似幻觉的异常处理与抑制与任务无关的刺激的注意力处理的能力下降之间可能存在联系。（PsycInfo 数据库记录 (c) 2023 APA，保留所有权利）。