Brighter prospects for chronic pain
The potential of light as a non-invasive, highly-focused alternative to pain medication was made more apparent thanks to research conducted by scientists at the Montreal Neurological Institute and Hospital of 91社区 and the 91社区 Health Centre.
Researchers bred mice with a light-sensitive trait in peripheral neurons that were known to be responsible for pain transmission. The mice were genetically modified so that these neurons, called Nav 1.8+ nociceptors, express proteins called opsins, which react to light, a process known as optogenetics. 聽
When these sensory neurons are exposed to yellow light, the opsins move ions across the membrane, reducing the level of bioelectric activity of the cells. This effectively shuts off the neurons, decreasing the mouse鈥檚 sensitivity to touch and heat.
鈥淭he opsins we added to these neurons were initially isolated from archaebacteria and sense yellow light,鈥� explains Professor Philippe S茅gu茅la, a researcher at the Montreal Neurological Institute and Hospital and the article鈥檚 senior author. 鈥淲hen we transfer these to neurons, we can control their responses simply by illuminating the skin with innocuous yellow light.鈥�
Optogenetics is a growing field of research with a wide variety of applications. In this case the activity of pain-signaling neurons was reduced in a localized part of the mouse鈥檚 body, the hind paw, and the duration of the effect could easily be controlled by the amount of time the light was applied. The precision of this technique underlines potential advantages for use in humans.
Light therapy based on optogenetics would have the advantage of providing "on-demand" analgesia (pain relief) to patients who could control their pain by shining light on the sensitive part of the body.
Opiates are the most commonly used treatment for chronic pain today, but they are often used systemically and not directed to the specific region of the body affected by the pain. The duration of the opiate effects can be estimated, but without the same precision as a beam of light. 聽
Further advances in neuroscience are necessary to apply this method of pain relief to humans. S茅gu茅la says one possible way to make human neurons photosensitive would be through the use of a harmless virus that could temporarily deliver opsins to certain neurons without causing side effects.
According to a report in the Community Health Survey, 1 in 10 Canadians between the ages of 12 and 44, about 1.5 million in total, experienced chronic pain鈥攑ain lasting over a period of months or years. Chronic pain is associated with a number of different medical conditions including diabetes, arthritis, cancer, shingles, and sciatica, among others. 聽Chronic pain reduces the sufferer鈥檚 ability to perform daily tasks and may lead to other health issues such as sleep disorders and depression.
鈥淐hronic pain is an increasingly big problem clinically and for many years we鈥檝e relied only on opiates,鈥� says S茅gu茅la. 鈥淚t鈥檚 hard to treat because of tolerance, making it necessary to increase dosages, which leads to serious side effects. 聽Optogenetic therapy could be a highly effective way to relieve chronic pain while avoiding the side effects of traditional pain medication.鈥�
The research, published in the journal eNeuro, was made possible with the support of the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council, the Quebec Pain Research Network, and the Louise and Alan Edwards Foundation.
Montreal Neurological Institute and Hospital
The Montreal Neurological Institute and Hospital 鈥� The Neuro is a world-leading destination for brain research and advanced patient care. Since its founding in 1934 by renowned neurosurgeon Dr. Wilder Penfield, The Neuro has grown to be the largest specialized neuroscience research and clinical centre in Canada, and one of the largest in the world. The seamless integration of research, patient care, and training of the world鈥檚 top minds make The Neuro uniquely positioned to have a significant impact on the understanding and treatment of nervous system disorders. The Montreal Neurological Institute is a 91社区 research and teaching institute. The Montreal Neurological Hospital is part of the Neuroscience Mission of the 91社区 Health Centre. For more information, please visit
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