Replication studies play an essential role in corroborating research findings and ensuring that subsequent experimental works are interpreted correctly. A previously published paper indicated that the neurotransmitter glutamate, along with the compounds N-methyl-d-aspartate (NMDA) and d-(−)-2-amino-5-phosphonopentanoic acid (AP5), acts as positive allosteric modulators of inhibitory glycine receptors. The paper further suggested that this form of modulation would play a role in setting the spinal inhibitory tone and influencing sensory signaling, as spillover of glutamate onto nearby glycinergic synapses would permit rapid crosstalk between excitatory and inhibitory synapses. Here, we attempted to replicate this finding in primary cultured spinal cord neurons, spinal cord slice, and Xenopus laevis oocytes expressing recombinant human glycine receptors. Despite extensive efforts, we were unable to reproduce the finding that glutamate, AP5, and NMDA positively modulate glycine receptor currents. We paid careful attention to critical aspects of the original study design and took into account receptor saturation and protocol deviations such as animal species. Finally, we explored possible explanations for the experimental discrepancy. We found that solution contamination with a high-affinity modulator such as zinc is most likely to account for the error, and we suggest methods for preventing this kind of misinterpretation in future studies aimed at characterizing high-affinity modulators of the glycine receptor.

中文翻译：

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谷氨酸，d-（-）-2-氨基-5-膦基戊酸和N-甲基-d-天冬氨酸不能直接调节甘氨酸受体

复制研究在证实研究结果和确保正确解释后续实验工作中起着至关重要的作用。以前发表的论文指出，神经递质谷氨酸，与化合物一起Ñ甲基d天冬氨酸（NMDA）和d-（-）-2-氨基-5-膦基戊酸（AP5）充当抑制性甘氨酸受体的正变构调节剂。该论文进一步建议，这种形式的调节将在设定脊柱抑制音调和影响感觉信号中发挥作用，因为谷氨酸溢出到附近的甘氨酸能突触上将允许兴奋性突触和抑制性突触之间快速串扰。在这里，我们试图在原代培养的脊髓神经元，脊髓切片和非洲爪蟾中复制这一发现。表达重组人甘氨酸受体的卵母细胞。尽管付出了巨大的努力，但我们无法重现谷氨酸，AP5和NMDA对甘氨酸受体电流有正向调节作用的发现。我们特别注意了原始研究设计的关键方面，并考虑了受体饱和度和实验方案偏差（例如动物物种）。最后，我们探索了实验差异的可能解释。我们发现，高亲和力调节剂（如锌）污染溶液最有可能解决该错误，并且我们在旨在表征甘氨酸受体高亲和力调节剂的未来研究中提出了防止这种误解的方法。