Dong Xiaoxi, Liu Tianjun, Wang Han, Yang Jichun, Chen Zhuying, Hu Yong, Li Yingxin
Chinese Academy of Medical Science & Peking Union Medical College, Institute of Biomedical Engineering, 236Baidi Road, Tianjin, China.
Department of Orthopaedics and Traumatology, The University of Hong Kong, QMH504 Professiorial Blk, Hong Kong, China.
Lasers Med Sci. 2017 Jul;32(5):1001-1008. doi: 10.1007/s10103-017-2200-3. Epub 2017 May 20.
This study aimed to develop a new laser stimulator to elicit both transient and sustained heat stimulation with a dual-wavelength laser system as a tool for the investigation of both transient and tonic experimental models of pain. The laser stimulator used a 980-nm pulsed laser to generate transient heat stimulation and a 1940-nm continuous-wave (CW) laser to provide sustained heat stimulation. The laser with 980-nm wavelength can elicit transient pain with less thermal injury, while the 1940-nm CW laser can effectively stimulate both superficial and deep nociceptors to elicit tonic pain. A proportional integral-derivative (PID) temperature feedback control system was implemented to ensure constancy of temperature during heat stimulation. The performance of this stimulator was evaluated by in vitro and in vivo animal experiments. In vitro experiments on totally 120 specimens fresh pig skin included transient heat stimulation by 980-nm laser (1.5 J, 10 ms), sustained heat stimulation by 1940-nm laser (50-55 °C temperature control mode or 1.5 W, 5 min continuous power supply), and the combination of transient/sustained heat stimulation by dual lasers (1.5 J, 10 ms, 980-nm pulse laser, and 1940-nm laser with 50-55 °C temperature control mode). Hemoglobin brushing and wind-cooling methods were tested to find better stimulation model. A classic tail-flick latency (TFL) experiment with 20 Wistar rats was used to evaluate the in vivo efficacy of transient and tonic pain stimulation with 15 J, 100 ms 980-nm single laser pulse, and 1.5 W constant 1940-nm laser power. Ideal stimulation parameters to generate transient pain were found to be a 26.6 °C peak temperature rise and 0.67 s pain duration. In our model of tonic pain, 5 min of tonic stimulation produced a temperature change of 53.7 ± 1.3 °C with 1.6 ± 0.2% variation. When the transient and tonic stimulation protocols were combined, no significant difference was observed depending on the order of stimuli. Obvious tail-flick movements were observed. The TFL value of transient pain was 3.0 ± 0.8 s, and it was 4.4 ± 1.8 s for tonic pain stimulation. This study shows that our novel design can provide effective stimulation of transient pain and stable tonic pain. Furthermore, it can also provide a reliable combination of transient and consistent stimulations for basic studies of pain perception.
本研究旨在开发一种新型激光刺激器，利用双波长激光系统引发瞬态和持续热刺激，作为研究疼痛瞬态和紧张性实验模型的工具。该激光刺激器使用980纳米脉冲激光产生瞬态热刺激，使用1940纳米连续波（CW）激光提供持续热刺激。980纳米波长的激光能引发瞬态疼痛且热损伤较小，而1940纳米连续波激光能有效刺激浅层和深层伤害感受器以引发紧张性疼痛。实施了比例积分微分（PID）温度反馈控制系统，以确保热刺激期间温度恒定。通过体外和体内动物实验评估了该刺激器的性能。对总共120个新鲜猪皮标本进行的体外实验包括：用980纳米激光进行瞬态热刺激（1.5焦耳，10毫秒）、用1940纳米激光进行持续热刺激（50 - 55°C温度控制模式或1.5瓦，5分钟连续供电）以及双激光瞬态/持续热刺激组合（1.5焦耳，10毫秒，980纳米脉冲激光，以及50 - 55°C温度控制模式的1940纳米激光）。测试了血红蛋白涂抹和风冷方法以找到更好的刺激模型。用20只Wistar大鼠进行经典甩尾潜伏期（TFL）实验，以评估15焦耳、100毫秒980纳米单激光脉冲以及1.5瓦恒定1940纳米激光功率下瞬态和紧张性疼痛刺激的体内效果。发现产生瞬态疼痛的理想刺激参数为峰值温度升高26.6°C和疼痛持续时间0.67秒。在我们的紧张性疼痛模型中，5分钟的紧张性刺激产生的温度变化为53.7±1.3°C，变化率为1.6±0.2%。当瞬态和紧张性刺激方案组合时，根据刺激顺序未观察到显著差异。观察到明显的甩尾动作。瞬态疼痛的TFL值为3.0±0.8秒，紧张性疼痛刺激的TFL值为4.4±1.8秒。本研究表明，我们的新颖设计能够有效刺激瞬态疼痛并稳定引发紧张性疼痛。此外，它还能为疼痛感知的基础研究提供瞬态和持续刺激的可靠组合。
