Investigation of NMDA receptor antagonist as antidepressant in animals

我们最近的双盲临床试验表明，氯胺酮（一种NMDA拮抗剂）在对典型抗抑郁药物治疗有抵抗力的患者中产生快速起效、强效和长效的抗抑郁作用。我们假设靶向AMPA/NMDA受体吞吐量是快速缓解抑郁症状的有效策略。为了进一步验证AMPA/NMDA通量假说，并基于这种氯胺酮现象开发新的药物，我们进行了一系列动物实验。我们发现亚麻醉剂量的氯胺酮治疗在两种行为范式，习得性无助测试和强迫游泳测试中产生快速起效的抗抑郁样作用。单次服药后，效果至少持续一周以上。MK-801（二唑西平）和NR2B选择性拮抗剂Ro25-6981也具有抗抑郁样作用；然而，这些效果没有氯胺酮持续的时间长。用氯胺酮治疗的动物在学习无助试验中表现良好，因此氯胺酮在动物身上的抗抑郁作用不太可能是由于使用氯胺酮导致的学习和记忆退化。在强迫游泳试验中，用AMPA受体拮抗剂NBQX预处理可以阻断氯胺酮-、MK-801-和ro25 -6981诱导的不动减少，表明这些药物的抗抑郁样作用需要AMPA通量。氯胺酮改变了氯胺酮处理动物海马组织中GluR1的磷酸化，NBQX预处理也阻断了这一作用。综上所述，我们的动物研究结果有力地支持AMPA受体参与氯胺酮的抗抑郁样作用，以及AMPA/NMDA通量策略开发新型抗抑郁药物。未来的研究需要进一步阐明受体亚型和参与这种氯胺酮类抗抑郁作用的大脑区域。为了进一步研究GluR1在氯胺酮抗抑郁样行为效应中的作用，我们获得了GluR1 KO小鼠并进行了表型分析。小鼠表现出严重的基线多动、不动和学习记忆缺陷，因此这些小鼠不适合在强迫游泳试验和习得性无助范式中测试GluR1消融是否会减弱氯胺酮诱导的抗抑郁药物样效应。

Our recent double blind clinical trials demonstrated that ketamine (an NMDA antagonist) produced rapid onset, robust, and long-pasting antidepressive actions in the patients who are resistant to typical antidepressant treatment. We have hypothesized that targeting AMPA/NMDA receptor throughput is an effective strategy for rapid relief of depression symptoms. To further test the AMPA/NMDA throughput hypothesis and to develop new medication based on this ketamine phenomenon, we conducted a series of animal experiments. We found that subanesthetic doses of ketamine treatment produced rapid onset antidepressant-like effects in two behavioral paradigms, the learned helpless test and the forced swim test. The effects lasted at least more than a week after a single drug administration. MK-801 (dizocilpine) and Ro25-6981, a NR2B selective antagonist, also exerted antidepressant-like effects; these effects, however, were not sustained as long as those of ketamine. Animals treated with ketamine in a similar regiment to the learned helpless test performed well on passive avoidance tests, thus the antidepressant-like effects of ketamine in animal is unlikely due to learning and memory deterioration associated with ketamine use. Pre-treatment with NBQX, an AMPA receptor antagonist, blocked ketamine-, MK-801- and Ro25-6981-induced immobility reductions in the forced swim test, indicating the antidepressant-like effects of these agents require AMPA throughput. Ketamine altered GluR1 phosphorylation in hippocampal tissues from ketamine treated animals, the effects was also blocked by NBQX pretreatment. Taken together, our animal findings strongly support the involvement of AMPA receptors in ketamine_s antidepressant-like action and the AMPA/NMDA throughput strategy to develop novel antidepressive agents. Future studies are required to further elucidate the receptor subtype(s) and the brain region(s) involved in this ketamine antidepressant-like action. To further examine the role of GluR1 in antidepressant-like behavioral effects of ketamine, the GluR1 KO mice were obtained and phenotyped. The mice showed profound baseline hyperactivity, in-immobility and learning and memory deficit, therefore these mice are not suitable for testing whether GluR1 ablation diminish ketamine-induced antidepressant like-effects in the forced swim tests and in the learned helplessness paradigm. Currently, we are investigating whether phosphorylation of GluR1 involves in ketamine-induced antidepressant like-effects. We tested a peptide which selectively blocks GluR1 phosphorylation. We will infuse this peptide to the brain of rat and evaluate the antidepressant like-effects of ketamine in the infused animal. We are also phenotyping the GluR1 phospho-mutant mice. The antidepressant like-effects of ketamine will also be examined in these mutant mice. Future studies are required to further elucidate the involvement of other AMPA and NMDA receptors and brain regions in this ketamine antidepressant-like action.