Investigation of neural mechanisms of 670 and 830nm laser acupuncture in pain relief, using rat

慢性疼痛很常见，每年在澳大利亚造成100亿美元的损失。药物治疗被广泛使用，但严重的副作用限制了使用。患者积极寻求非药物治疗，激光针灸是慢性疼痛最常见的治疗方法之一，然而，它的工作原理尚不清楚。研究人员提出，激光针灸通过直接作用于神经，改变疼痛信号传递到大脑的方式来减轻疼痛。为了研究这一点，我们（CI A和CI B）先前进行了红外激光对神经细胞培养的研究。在此之前，CI b进行了一项积极的临床研究，使用相同波长的激光治疗颈部疼痛。我们确定激光暂时中断神经运输系统，该系统由一系列微小的管组成，称为微管。这些细胞作为线粒体运输的“单轨”系统，为所有神经功能提供能量。我们提出，这个系统的暂时中断，称为快速轴突运输，破坏沿神经疼痛信号的传导，导致疼痛缓解。830nm激光针刺在临床上减轻疼痛的机制尚不清楚。为了使其进入主流临床实践，确定激光对周围神经特别是疼痛传导纤维的影响是很重要的。我们从早期的一项研究中得知，单次暴露会导致疼痛纤维发生显著但可逆的变化，包括轴突微管破坏、线粒体膜电位降低和轴突快速流动阻断。这些事件会导致传导失效。问题是，与临床治疗相比，重复照射是否会导致同样的变化。这将为了解激光针灸的临床疗效提供科学依据。我们也不知道670nm激光针灸是否会起到同样的作用。有证据表明，这可能更有效，所以这仍然是另一个重要的悬而未决的问题。此外，没有证据表明哪种波长在成本和时间上是有效的，因为希望提供更低的剂量。我们需要确定最有效的剂量和波长，以便进行临床试验，就像CIB为试验所做的那样（Chow和Barnsley， 2006）。

Background Chronic pain is common and costs $10 billion dollars per year in Australia. Drug therapies are widely used but serious side effects limit use. Patients actively seek non-drug treatments and laser acupuncture is one of the most commonly sought therapies for chronic pain, however, how it works is not well understood. Our previous work Researchers propose that laser acupuncture reduces pain by direct effects on nerves, altering how pain signals are transmitted to the brain. To investigate this we (CI A and CI B) previously undertook a study of infrared laser on nerve cell cultures. This followed on from a positive clinical study with the same laser wavelength in the treatment of neck pain, undertaken by CI B. We established that laser temporarily interrupts the nerve transport system, which is made up of a series of minute tubes, called microtubules. These act as a “monorail” system for transport of mitochondria, which provide energy for all nerve functions. We propose that temporary interruption of this system, called fast axonal transport, disrupts the conduction of pain signals along the nerve, resulting in pain relief. Important unanswered questions The mechanism by which 830nm laser acupuncture relieves pain clinically remains poorly understood. For its acceptance into mainstream clinical practice it is important to determine the effect of laser on the peripheral nerves and in particular the pain carrying fibres. We know from an earlier study that a single exposure causes significant but reversible changes in pain fibres including axonal microtubule disruption, decrease in mitochondrial membrane potential and block of fast axonal flow. These events would result in conduction failure. The question is whether the repeated irradiations, comparable to those delivered clinically result in the same changes. This would provide a scientific basis for understanding the clinical effectiveness of laser acupuncture. We also do not know if 670nm laser acupuncture would act in the same way. There is evidence that this may be more effective so that this remains another important unanswered question. Further, there is no evidence regarding which wavelength would be cost and time effective as it is desirable to deliver lower dose. We need to determine the most effective dose and wavelength so that clinical trials could be carried out as was done for the trials by CIB (Chow and Barnsley, 2006).