Abstract：
BACKGROUND: Exaggerated responses to sensory stimuli, a hallmark of Fragile X syndrome (FXS), contribute to anxiety and learning challenges. Sensory hypersensitivity is recapitulated in the Fmr1 knockout (KO) mouse model of FXS. Recent studies in Fmr1 KO mice have demonstrated differences in activity of cortical interneurons and a delayed switch in the polarity of GABA signaling during development. Previously, we reported that blocking the chloride transporter NKCC1 with the diuretic bumetanide, could rescue synaptic circuit phenotypes in primary somatosensory cortex (S1) of Fmr1 KO mice. However, it remains unknown whether bumetanide can rescue earlier circuit phenotypes or sensory hypersensitivity in Fmr1 KO mice.
METHODS: We used acute and chronic systemic administration of bumetanide in Fmr1 KO mice and performed in vivo 2-photon calcium imaging to record neuronal activity, while tracking mouse behavior with high-resolution videos.
RESULTS: We demonstrate that layer (L) 2/3 pyramidal neurons in S1 of Fmr1 KO mice show a higher frequency of synchronous events at postnatal day (P) 6 compared to wild-type controls. This was reversed by acute administration of bumetanide. Furthermore, chronic bumetanide treatment (P5-P14) restored S1 circuit differences in Fmr1 KO mice, including reduced neuronal adaptation to repetitive whisker stimulation, and ameliorated tactile defensiveness. Bumetanide treatment also rectified the reduced feedforward inhibition of L2/3 neurons in S1 and boosted the circuit participation of parvalbumin interneurons.
CONCLUSIONS: This further supports the notion that synaptic, circuit, and sensory behavioral phenotypes in Fmr1 KO can be mitigated by inhibitors of NKCC1, such as the FDA-approved diuretic bumetanide.
METHODS: We used acute and chronic systemic administration of bumetanide in Fmr1 KO mice and performed in vivo 2-photon calcium imaging to record neuronal activity, while tracking mouse behavior with high-resolution videos.
RESULTS: We demonstrate that layer (L) 2/3 pyramidal neurons in S1 of Fmr1 KO mice show a higher frequency of synchronous events at postnatal day (P) 6 compared to wild-type controls. This was reversed by acute administration of bumetanide. Furthermore, chronic bumetanide treatment (P5-P14) restored S1 circuit differences in Fmr1 KO mice, including reduced neuronal adaptation to repetitive whisker stimulation, and ameliorated tactile defensiveness. Bumetanide treatment also rectified the reduced feedforward inhibition of L2/3 neurons in S1 and boosted the circuit participation of parvalbumin interneurons.
CONCLUSIONS: This further supports the notion that synaptic, circuit, and sensory behavioral phenotypes in Fmr1 KO can be mitigated by inhibitors of NKCC1, such as the FDA-approved diuretic bumetanide.
摘要：
背景：对感官刺激的反应夸张，脆性X综合征（FXS）的标志，有助于焦虑和学习挑战。在FXS的Fmr1敲除(KO)小鼠模型中概括了感觉超敏反应。Fmr1KO小鼠的最新研究表明，皮层中间神经元的活性差异以及发育过程中GABA信号极性的延迟转换。以前,我们报道了用利尿剂布美他尼阻断氯化物转运蛋白NKCC1，可以挽救Fmr1KO小鼠初级体感皮层（S1）的突触回路表型。然而,目前尚不清楚布美他尼是否能挽救Fmr1KO小鼠早期的回路表型或感觉超敏反应.
方法：我们在Fmr1KO小鼠中使用了布美他尼的急性和慢性全身给药，并进行了体内2光子钙成像以记录神经元活动，同时使用高分辨率视频跟踪鼠标行为。
结果：我们证明，与野生型对照相比，Fmr1KO小鼠S1的层（L）2/3锥体神经元在出生后第6天（P）显示出更高的同步事件频率。这通过急性施用布美他尼来逆转。此外，慢性布美他尼治疗（P5-P14）恢复了Fmr1KO小鼠的S1回路差异，包括减少神经元对重复胡须刺激的适应，和改善触觉防御。布美他尼治疗还纠正了S1中L2/3神经元的前馈抑制减少，并增强了小白蛋白中间神经元的回路参与。
结论：这进一步支持了突触，电路,Fmr1KO的感觉行为表型可以通过NKCC1的抑制剂来缓解,如FDA批准的利尿剂布美他尼.
方法：我们在Fmr1KO小鼠中使用了布美他尼的急性和慢性全身给药，并进行了体内2光子钙成像以记录神经元活动，同时使用高分辨率视频跟踪鼠标行为。
结果：我们证明，与野生型对照相比，Fmr1KO小鼠S1的层（L）2/3锥体神经元在出生后第6天（P）显示出更高的同步事件频率。这通过急性施用布美他尼来逆转。此外，慢性布美他尼治疗（P5-P14）恢复了Fmr1KO小鼠的S1回路差异，包括减少神经元对重复胡须刺激的适应，和改善触觉防御。布美他尼治疗还纠正了S1中L2/3神经元的前馈抑制减少，并增强了小白蛋白中间神经元的回路参与。
结论：这进一步支持了突触，电路,Fmr1KO的感觉行为表型可以通过NKCC1的抑制剂来缓解,如FDA批准的利尿剂布美他尼.
