Rescue of cortical inhibitory synapses following developmental hearing loss

项目总结 听力损失(HL)是儿童最常见的感觉障碍，存在听力障碍的风险。 沟通。此外，即使在听力恢复正常后，这些缺陷也会持续存在，这表明 发育性HL永久性损害中枢突触功能，损害听觉。在……里面 事实上，沙土鼠的短暂性HL导致知觉缺陷，这与抑制性突触减少密切相关 听觉皮质的强度(ACX)(Caras&Sanes，2015；Mowery等人)。2015、2016)。此外，这一赤字是 由于GABAA和GABAB受体介导的抑制作用均丧失。因此，这项提议探索了一个因果关系 抑制减弱与知觉缺陷之间的关系。我们的核心假设是发育 听力损失导致突触后GABAA和GABAB受体介导的抑制在 听觉皮质，从而导致知觉缺陷。三个目标检验由此产生的预测 假设：目的1验证GABAA和GABAB受体介导的抑制性突触后突触的预测 在HL后，必须挽救每个电位(IPSP)以恢复正常的抑制强度。沙鼠将被饲养 在出生后11-23天使用暂时性双侧HL(耳塞)，并每天注射a 这一时期的GABA能增强剂。动物将被饲养到成年(&gt；p86)，听力正常， 光遗传学方法将用于评估脑片中的GABAA和GABAB IPSP。为了评估- 目标效应，将测量EPSPS和放电特性。将与车辆进行比较- 治疗HL和对照动物。Aim 2测试HL诱导的抑制减弱是固有的 ACX锥体细胞。沙土鼠将从P11-23用HL饲养，然后ACX层2/3锥体细胞将 用编码GABA受体亚单位或运输蛋白的基因转染，每一种都从 新获得的沙土鼠基因组序列。如目标1所示，对IPSP、EPSP和 放电特性将从成人ACX获得。Aim 3测试了知觉缺陷可以是 通过挽救ACX突触抑制而恢复。沙土鼠将从P11-23开始用HL饲养，并接受以下任一治疗： 每日注射有效的GABA增强子(目标1)，或用有效载体ACX转染(目标2)。 动物随后将接受幅度调制(AM)检测任务的测试，以获得心理测量阈值。 为了确定知觉是否与抑制强度相关，对IPSP的光遗传学评估将 都是从相同的动物身上获得的。这项提案的创新之处在于：(I)合作对沙鼠进行排序 (Ii)成人ACX突触的高通量分析 利用光遗传学发挥功能，以及(Iii)强调GABAB受体在发育障碍中的作用。 总之，这项提议的意义在于确定和补救有助于 儿童期HL的知觉缺陷。如果成功，该项目将为 教育障碍持续存在于患有HL的儿童中，这与耳蜗病理是分开的。

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.