Electrochemical assessment of behaviorally relevant circuit function after TBI

项目摘要/摘要 创伤性脑损伤(TBI)经常导致持续的创伤后神经后果， 包括对光过敏，但有效的治疗方法有限。视觉是人类的一种主要的感觉方式 人类，类似于啮齿类动物的胡须感觉。初级感觉模式结合了很大一部分 大脑进行处理，使他们容易受到弥漫性脑损伤。这项提案的目标是雇用一名 弥漫性脑损伤的实验性啮齿动物模型，突出感觉缺陷以评估迟发性改变 谷氨酸信号作为脑损伤的普遍结果及其调节的可能性。在中使用此模型 PI的初步结果表明，脑外伤可诱导迟发性胡须感觉过敏 伤后刺激日(PID)28，持续到PID56。这种由伤害引起的感觉过敏是 使用已建立的胡须滋扰任务(WNT)进行测量，其中胡须刺激导致活动 受伤大鼠的逃避和异常反应与未受伤大鼠的矛盾心理或好奇心相比较。自.以来 晶须电路是谷氨酸能的，这个研究小组实现了电化学微电极阵列 能够实时测量体内谷氨酸神经传递的技术，用于记录 麻醉大鼠胡须环路的继电器。PI报告说，WNT分数与 钾(KCl)引起的体感丘脑和皮质谷氨酸释放的幅度。 诱发的谷氨酸释放对Ω-芋螺毒素敏感，提示突触前谷氨酸超敏 释放作为胡须过敏的潜在机制。此外，神经元形态的三维重建 显示在PID28的丘脑内终末树突的数量增加，提供了一个潜在的来源 增加谷氨酸的释放。麻醉研究中需要KCL诱发的谷氨酸反应，因为 触须刺激引起的谷氨酸反应被麻醉抑制。因此，实时录制的 清醒、自由活动的大鼠的谷氨酸神经传递允许评估胡须刺激- 在WNT期间诱发谷氨酸反应。这导致了脑损伤诱导的中心假设 感觉超敏是由于感觉回路中谷氨酸信号的改变以及早期康复 将恢复电路功能并缓解行为症状。为了检验这些假设，成年男性和女性 采用中线液压冲击致大鼠弥漫性颅脑损伤模型，观察性别对大鼠脑损伤的影响。 迟发性感觉超敏反应与谷氨酸神经传递；2)胡须 清醒、自由活动大鼠受刺激诱发的谷氨酸释放与弥漫性脑损伤后时间的关系，以及3) 有证据表明，以胡须为重点的电路定向康复可以缓解谷氨酸过敏 释放和同时发生的行为感官过敏。影响：将这种电路中断模型结合起来 通过在清醒的自由活动的大鼠中进行电化学记录，可以评估谷氨酸信号作为一种 用于评估治疗方法的损伤引起的持续性神经功能缺陷的生物标志物。

Project Summary/Abstract Traumatic brain injuries (TBI) frequently result in persisting post-traumatic neurological consequences, including hypersensitivity to light, with limited effective treatments. Vision is a primary sensory modality in humans, similar to whisker sensation in rodents. Primary sensory modalities incorporate a large portion of the brain for processing, making them susceptible to diffuse TBI. The goal of this proposal is to employ an experimental rodent model of diffuse TBI that highlights sensory deficits to evaluate delayed alterations in glutamate signaling as a universal consequence of TBI and its potential for modulation. Using this model in preliminary results the PI has demonstrated that TBI induces late-onset sensory hypersensitivity to whisker stimulation by post-injury day (PID) 28 that persists to PID 56. This injury-induced sensory hypersensitivity is measured using the established Whisker Nuisance Task (WNT), where whisker stimulation results in active evasion and aberrant responses in injured rats compared to ambivalence or curiosity in uninjured rats. Since the whisker circuit is glutamatergic, this research team implemented electrochemical microelectrode array technology, capable of real-time measurements of glutamate neurotransmission in vivo, for recordings within the relays of the whisker circuit in anesthetized rats. The PI reported that WNT scores positively correlate to the magnitude of potassium (KCl)-evoked glutamate release in the somatosensory thalamus and cortex. Evoked-glutamate release was sensitive to Ω-conotoxin, indicating hypersensitive presynaptic glutamate release as a potential mechanism for whisker hypersensitivity. Also, 3D reconstruction of neuron morphology shows increased numbers of terminating dendrites within the thalamus at PID 28, providing a potential source for increased glutamate release. KCl-evoked glutamate responses are required in anesthetized studies since whisker stimulation-evoked glutamate responses are suppressed by anesthesia. Thus, real-time recordings of glutamate neurotransmission in the awake, freely-moving rat permits the evaluation of whisker stimulation- evoked glutamate responses during the WNT. This has led to the central hypotheses that TBI-induced sensory hypersensitivity arises from altered glutamate signaling in sensory circuits and that early rehabilitation will restore circuit function and alleviate behavioral symptoms. To test these hypotheses adult male and female rats will be subjected to diffuse TBI by midline fluid percussion and evaluated for: 1) the influence of sex on late-onset sensory hypersensitivity to whisker stimulation and glutamate neurotransmission; 2) whisker stimulated-evoked glutamate release in awake, freely-moving rats, with respect to time post-diffuse TBI, and 3) evidence that circuit-directed rehabilitation, focused on the whiskers, can mitigate hypersensitive glutamate release and concurrent behavioral sensory hypersensitivity. Impact: Coupling this model of circuit disruption with electrochemical recordings in awake, freely-moving rats allows for evaluation of glutamate signaling as a biomarker for injury-induced persisting neurological deficits for evaluation of therapeutic approaches.