Rescue of cortical inhibitory synapses following developmental hearing loss

项目摘要 听力损失（HL）是最常见的儿童感觉障碍，造成听力障碍的风险。 通信此外，这些缺陷甚至在正常听觉恢复后仍会持续，这表明， 发育性HL永久性地损害损害听觉感知的中枢突触功能。在 事实上，沙鼠的短暂HL诱导的知觉缺陷与抑制性突触减少密切相关。 听觉皮质强度（ACx）（卡拉斯和萨内斯，2015; Mowery等人，2015，2016）。此外，这一赤字 这是由于GABAA和GABAB受体介导的抑制作用丧失所致。因此，本提案探讨了一种因果关系， 抑制减弱和知觉缺陷之间的关系。我们的核心假设是， 听力损失诱导突触后GABAA和GABAB受体介导的抑制减少， 听觉皮层，从而导致知觉缺陷。三个目标测试由此产生的预测 假设：目的1检验GABAA和GABAB受体介导的抑制性突触后神经元的预测。 在HL后，必须分别挽救IPSP以恢复正常的抑制强度。沙鼠将被饲养 从出生后（P）11-23天暂时性双侧HL（耳塞），并接受每日注射a GABA能增强剂在此期间。然后将动物饲养至具有正常听力的成年期（>P86）， 并且光遗传学方法将用于评估脑切片中的GABAA和GABAB IPSP。去评估- 将测量目标效果、EPSP和放电特性。将与车辆进行比较- 处理的HL和对照动物。目的2检验HL诱导的抑制性减弱是 ACx锥体细胞。将用HL从P11- 2/3饲养沙鼠，然后将ACx层2/3锥体细胞 用编码GABA受体亚单位或运输蛋白的基因转染，每种基因得自 沙鼠基因组序列如在目标1中一样，IPSP、EPSP和EPSP的光遗传学评估被称为光遗传学评估。 将从成人ACx获得放电特性。目标3测试了感知缺陷可能 通过挽救ACx突触抑制而恢复。从P11-23开始，长爪沙鼠将使用HL饲养，并接受： 每日注射有效的GABA增强剂（Aim 1），或用有效载体进行ACx转染（Aim 2）。 然后对动物进行幅度调制（AM）检测任务测试，以获得心理测量阈值。 为了确定感知是否与抑制强度相关，IPSP的光遗传学评估将 从相同的动物身上获得。该提案的创新之处在于：（i）合作对沙鼠进行测序 基因组，并配备载体与沙鼠特异性基因，（ii）高通量测定成人ACx突触 功能使用光遗传学，和（iii）强调GABAB受体在发育障碍中的作用。 总之，这一建议的重要性是确定和补救一个CNS机制，有助于 伴随儿童HL的知觉缺陷。如果成功，该项目将为 与耳蜗病理学无关的HL儿童中持续存在的教育障碍。

PROJECT SUMMARY Hearing loss (HL) is the most prevalent childhood sensory impairment, posing a risk for deficits in aural communication. Moreover, these deficits can persevere even after normal audibility returns, suggesting that developmental HL permanently impairs central synapse function which compromises auditory perception. In fact, transient HL in gerbils induces perceptual deficits that are well-correlated with reduced inhibitory synaptic strength in auditory cortex (ACx) (Caras & Sanes, 2015; Mowery et al. 2015, 2016). Furthermore, this deficit is due to loss of both GABAA and GABAB receptor-mediated inhibition. Therefore, this proposal explores a causal relationship between weakened inhibition and perceptual deficits. Our core hypothesis is that developmental hearing loss induces a reduction of both postsynaptic GABAA- and GABAB receptor-mediated inhibition within auditory cortex, thereby causing perceptual deficits. Three aims test predictions that emerge from this hypothesis: Aim 1 tests the prediction that GABAA- and GABAB receptor-mediated inhibitory postsynaptic potentials (IPSP) must each be rescued to regain normal inhibitory strength following HL. Gerbils will be reared with transient bilateral HL (earplugs) from postnatal (P) days 11-23, and receive daily injections of a GABAergic enhancer during this period. Animals will then be reared to adulthood (>P86) with normal hearing, and an optogenetic approach will be used to assess GABAA and GABAB IPSPs in brain slices. To assess off- target effects, both EPSPs and discharge properties will be measured. Comparisons will be made to vehicle- treated HL and control animals. Aim 2 tests the prediction that HL-induced inhibitory weakening is intrinsic to ACx pyramidal cells. Gerbils will be reared with HL from P11-23, and ACx layer 2/3 pyramidal cells will then be transfected with genes that encode GABA receptor subunits or trafficking proteins, each obtained from the newly available gerbil genome sequence. As in Aim 1, optogenetic assessment of IPSPs, EPSPs, and discharge properties will be obtained from adult ACx. Aim 3 tests the prediction that perceptual deficits can be restored by rescuing ACx synaptic inhibition. Gerbils will be reared with HL from P11-23 and receive either: daily injections an effective GABA enhancer (Aim 1), or ACx transfection with an effective vector (Aim 2). Animals will then be tested on an amplitude modulation (AM) detection task to obtain psychometric thresholds. To determine whether perception correlates with inhibitory strength, an optogenetic assessment of IPSPs will be obtained from the same animals. Innovations in this proposal are: (i) collaborations to sequence the gerbil genome and to equip vectors with gerbil-specific genes, (ii) a high throughput assay of adult ACx synapse function using optogenetics, and (iii) an emphasis on the role of GABAB receptors in developmental disorders. Together, the significance of this proposal is to identify and remediate a CNS mechanism that contributes to the perceptual deficits that attend childhood HL. If successful, the project will provide one explanation for the educational barriers that persist in children with HL that is separate from cochlear pathology.