Systematic characterization of spinal cord stimulation effects on dorsal horn populations

有必要了解神经调节疗法的基本生物学机制，以改善临床交付和结果(RFA-NS-20-006)。顽固性慢性背部和四肢疼痛的临床治疗仍然具有挑战性，脊髓刺激(SCS)设备尽管缺乏公认的机械基础，但仍经历了巨大的市场增长。对SCS如何参与背角电路的了解很少，主要是由于与传统电生理记录相关的技术限制，如刺激诱导的电噪声伪迹和低采样功率。多光子显微镜提供了一种新的和强大的方法来表征干细胞调控的转基因小鼠的背角回路，转基因小鼠的基因工程是为了在分子定义的群体中表达钙指示剂。一个可植入的微型双极SCS电极将被用来研究浅层背角人群的整个临床相关刺激参数的频谱。我们将调查各种频率、占空比和波形。初步实验表明，在GABA能群体中，50赫兹的SCS优先驱动持续放电。我们计划系统地描述刺激参数对GABA能(目标1)和谷氨酸能(目标2)种群的影响。SCS电极的远端和近端的神经元网络将被检查，允许分别量化背柱和电场介导的影响。伤害性传入通路的刺激将与SCS相结合，以表征标记的输出投射神经元的反应，无论是在体外还是在植入了慢性成像窗口的完整小鼠中(目标3)。门控制理论认为，背柱的激活激活了LAMING II中的抑制性神经元；这一概念将在目标1中使用具有优越采样能力和不受刺激伪影影响的成像技术进行直接测试。这一方法将提供一个前所未有的了解SCS参数，包括能量传递，在较长时间内对背角神经元活动的影响。该项目的中心目标与RFA密切相关，通过提出实验来描述相关小鼠模型中细胞对神经刺激的反应，并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设备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.