It is a necessity that university students understand these therapeutic techniques that are widely used.
Hi Rolando,
This is an interesting question! I think you wouldn't be able to find many articles published on this subject. Thus, don't expect conclusive results:) I think it might be similar to stimulating acupuncture points but with light. It would require acting selectively on the point or the area around it. Here I'm on a thin ice, because the mechanism of stimulating/activating such points with light is not really known. I hope I've got your question right, and you're not talking about mechanisms of PDT (that is light activation of the drug and light-induced toxicity).
Dear Serge, thank you very much for the important contribution.
Dear Dr Ronaldo Serro Toledo
As you know although laser phototherapy has been used for years and many clinical trials have demonstrated the pain relieving effects of phototherapy in various pain syndromes, the real basic biological mechanisms behind these analgesic effects are not completely known yet. Some of the proposed explanations for these pain relieving effects are as follows:
• Reversible blockage of action potential generation of nociceptive signals in primary afferent neurons and specific reversible inhibition and functional impairment of Aδ and C fibers, which transmit nociceptive stimuli
• Increase in β-endorphin and other opioid peptide synthesis and release
• Inhibiting cyclooxygenase, interrupting conversion of arachidonic acid in to
prostaglandins, especially prostaglandin E2 (PGE2)
• Suppression of bradykinin activity, a pro-inflammatory neuropeptide that irritates
nociceptors and is a key element in clinical pain and the associated inflammation.
• Increased serotonin production, affecting negatively neurotransmission
• Increased synaptic activity of acetylcholine esterase
• Involvement of nitric oxide in analgesic effects of therapeutic lasers
• Single oxygen production, which in small amounts, is very important in biochemical processes and may be important in biostimulation
• Decreased inflammation and subsequently decreased inflammatory sensitization of small-diameter afferent nerve endings. In addition inflammatory decrease and consequently reducing edema decrease sensitization of pain receptors.
• Improvement of local microcirculation, increased tissue oxygenation, shift of
metabolism from anaerobic to aerobic pathways, decreased production of acidic
metabolites which stimulate the pain receptors
• Increased lymphatic flow and consequently reducing edema, which leads to decreased sensitization of pain receptors.
In addition some researchers propose that in addition to local laser analgesic effect, poorly understood systemic effects through the release of some metabolites might contribute in these effects too. These hypothesis complicate the understanding of the mechanisms more.
Certainly further basical studies are necessary to elucidate the exact mechanisms of interesting analgesic effect of laser phototherapy.
Dear Rolando & Nazrim
i appreciate the question and Nazrim's answer - i have been very interested in this topic lately. I have been carrying out a "1st person" science experiment (n=3 including self, dog and husband - all of whom are still alive after the experiment) and can attest for the point describing " decreased inflammation and subsequently decreased inflammatory sensitization of small-diameter afferent nerve endings. In addition inflammatory decrease and consequently reducing edema decrease sensitization of pain receptors." Given that my data are not enough for a peer review publication i will just say that i was skeptical to the use of LLLT until recently. One of my dogs was seriously ill and unable to move, in excruciating pain and diagnosed with back pain in cervical/toracic area. The dog was taking pain meds and lethargic, unable to walk, etc. After one treatment with a laser device (and immediately after) the dog walked out of the office with a completely different demeanor, wagging his tail for 1st time in 3 weeks. It lasted only a day and we took him to do other couple of treatments, improving more and more rapidly and effect lasting for longer. Dog completely recovered. I have been very interested all my life in the power f the placebo effect, but hard to explain how the placebo effect may work on dogs if this was a placebo effect at all. Because of the results i was willing to try myself on chronic pain issues (neck and low back) and can say the effects were clear and immediate. There seem to be some cummulative effect of treatments. Also the effects on lymphatic drainage feels similar to that i receive from swimming (n=1 personal observation - though i have found a peer review pub on the effect of LLLT on lymphedema which seems to agree with my perception). Hubby reported effects on improvement in peripheral neuropathy (again, n=1... but peer-review articles do report effect on pain and Nazrim answers seem to point at this one too.) This may not help you explain to your students, but perhaps will give you a better understanding of what this modallity can do.
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