Systematic characterization of spinal cord stimulation effects on dorsal horn populations

非常需要了解神经调节治疗的基本生物学机制，以改善临床治疗和结局（RFA-NS-20-006）。背部和四肢的顽固性慢性疼痛在临床治疗上仍然具有挑战性，尽管缺乏公认的机制基础，但脊髓刺激（SCS）器械已经经历了巨大的市场增长。关于SCS如何接合背角电路的知识很少，主要是由于与传统电生理记录相关的技术限制，例如刺激诱导的电噪声伪影和低采样功率。多光子显微镜提供了一种新颖且强大的方法来表征转基因小鼠中受SCS调节的背角回路，这些小鼠经过基因工程改造以在分子定义的群体中表达钙指示剂。将使用植入式微型双极SCS电极研究浅表背角群体的临床相关刺激参数的整个频谱。广泛的频率，占空比和波形将被调查。初步实验表明，SCS在50 Hz驱动持续放电优先GABA能人群。我们计划系统地表征刺激参数对GABA能（Aim 1）和谷氨酸能（Aim 2）群体的影响。将检查SCS电极远端和近端的神经元网络，从而分别量化背柱和电场介导的效应。传入通路的伤害感受性范围刺激将与SCS结合，以表征体外和植入慢性成像窗的完整小鼠中标记的输出投射神经元的反应（Aim 3）。门控理论表明，背柱的激活激活了位于Laming II中的抑制性神经元;这一概念将在Aim 1中使用具有上级采样能力且不受刺激伪影影响的成像技术进行直接测试。这种方法将提供一个前所未有的理解SCS参数的影响，包括能量输送，背角神经元的活动在很长一段时间。该项目的中心目标与RFA密切相关，通过提出实验来表征相关小鼠模型中对神经刺激的细胞反应，具有明确的翻译含义。这些研究的结果有望为下一代神经调节器械的设计和改进奠定基础，并对患者护理产生重大影响。

There is a substantial need to understand the fundamental biological mechanisms of neuromodulation therapies in order to improve clinical delivery and outcomes (RFA-NS-20-006). Intractable chronic pain of the back and limbs continues to be challenging to treat clinically, and spinal cord stimulation (SCS) devices have experienced tremendous market growth despite a lack of an accepted mechanistic basis. There is minimal knowledge of how SCS engages dorsal horn circuits, primarily due to technical limitations associated with traditional electrophysiological recordings, such as stimulation-induced electrical noise artifacts and low sampling power. Multiphoton microscopy provides a novel and powerful approach to characterize the dorsal horn circuits modulated by SCS in transgenic mice genetically engineered to express calcium indicators in molecularly defined populations. An implantable miniature bipolar SCS electrode will be utilized to study the entire spectrum of clinically-relevant stimulation parameters on superficial dorsal horn populations. A wide range of frequencies, duty cycles, and waveforms will be investigated. Preliminary experiments demonstrated that SCS at 50 Hz drives sustained firing preferentially in GABAergic populations. We plan to systematically characterize the effects of stimulation parameters on GABAergic (Aim 1) and glutamatergic (Aim 2) populations. Neuronal networks distal and proximal to the SCS electrode will be examined, allowing the quantification of dorsal column and electrical field mediated effects, respectively. Nociceptive-range stimulation of afferent pathways will be combined with SCS to characterize responses in labeled output projection neurons, both in vitro and in intact mice implanted with a chronic imaging window (Aim 3). The Gate Control Theory suggested that activation of dorsal columns activates inhibitory neurons residing in laming II; this notion will be directly tested in Aim 1 using imaging techniques with superior sampling power and impervious to stimulation artifacts. This approach will provide an unprecedented understanding of the impact of SCS parameters, including energy delivery, on the activity of dorsal horn neurons over prolonged periods. This project's central goals are closely aligned with the RFA by proposing experiments to characterize cellular responses to neurostimulation in a relevant mouse model, with clear translational implications. Findings from these studies are expected to lay the foundation for the design and refinement of next-generation neuromodulation devices and substantially impact patient care.