Wednesday, September 2, 2009

Secrets of Acupuncture for Pain Revealed – a Bit

Researchers at the University of Michigan Chronic Pain and Fatigue Research Center provide the first evidence of how acupuncture may relieve pain by enhancing the action of opioid receptors in the brain. However, this may not completely explain why sham (fake) acupuncture also seems to relieve pain.

Acupuncture has been used to treat pain for centuries, possibly by activating the body’s intrinsic painkillers (eg, endorphins), but how it works at the cellular level has been a mystery. In a recently-reported study, participants included 20 women who had been diagnosed with fibromyalgia and experienced pain at least 50% of the time. During the study they agreed not to take any new medications for their fibromyalgia pain [Harris et al. 2009]. The women were randomly assigned to receive either traditional Chinese acupuncture or sham acupuncture treatments during the course of 4 weeks. Brain imaging (positron emission tomography, or PET) was performed during the first treatment session and repeated a month later following the 8th treatment. Results showed that true acupuncture produced both short- and long-term increases in the binding availability of mu-opioid receptors (MOR) in multiple limbic regions of the brain that process and dampen pain signals (eg, cingulate, caudate, and amygdala); whereas, these effects were largely absent in the sham acupuncture group. “Interestingly, both acupuncture and sham acupuncture groups had reductions in clinical pain,” according to lead author, Richard E. Harris, PhD [in a press release], “but the mechanisms leading to pain relief are distinctly different.” Since opioid analgesics, such as morphine, work by binding to MORs, and those receptors bind opioids more effectively following acupuncture, an implication of this research is that patients with chronic pain treated with acupuncture might be more responsive to opioid medications, Harris suggests.

Commentary: This was a small study and the benefits of opioid analgesics for augmenting pain relief in patients treated with acupuncture were not tested. Furthermore, the study does not shed much light on controversies about sham acupuncture being as effective as real acupuncture in reducing chronic pain [eg, see here]. Meanwhile, an interesting and just-reported study examined brain function associated with “placebo analgesia” induced by sham therapy [Watson et al. 2009]. For this study, participants were administered pain-inducing laser stimulation on their forearms and, then, prior to a second round of painful laser stimuli they were told an anesthetic cream was being applied — in fact, however, they all received an inactive “sham” cream. Brain imaging (via functional magnetic resonance imaging, or fMRI) was performed during the experiment. The sham-cream treatment resulted in significant reductions in pain, and corresponding changes in brain activity were largely centered in prefrontal cortical areas (that is, “thinking areas” of the brain, as opposed to pain-modulating limbic structures noted in the acupuncture study above). The researchers suggest that the main placebo-analgesic effect came from a reduced anticipation of pain due to the (sham) therapy; in other words, participants thought and believed the cream would help so it did.

Relating back to the acupuncture studies, and this may be rather speculative, it seems plausible that acupuncture therapy (real or sham) may affect multiple brain regions. Whether treatment is applied with needles or dull sticks there are neurological processes at work, and a belief in the effectiveness of the treatment may be as potent in relieving pain as the influence on opioid receptors. This needs further study since it could have clinical relevance for various pain therapies.

References:
> Harris RE, Zubieta JK, Scott DJ, Napadow V, Gracely RH, Clauw DJ. Traditional Chinese acupuncture and placebo (sham) acupuncture are differentiated by their effects on mu-opioid receptors (MORs). NeuroImage. 2009;47(3),1077-1085 PMID: 19501658
> Watson A, El-Deredy W, Iannetti GD, et al. Placebo conditioning and placebo analgesia modulate a common brain network during pain anticipation and perception. Pain. 2009;145:24-30.


ADDENDUM — [1/23/2010] an interesting trial on this subject was reported last May 2009, finding that acupuncture was effective for low back pain; however, it was unclear whether real acupuncture versus simulated acupuncture was superior, or if both actually represented placebo effects. At one year posttreatment, patients receiving acupuncture (real or sham) were more likely than those receiving usual care (non-acupuncture) to have clinically meaningful improvements in dysfunction but not in symptom relief.
> Cherkin DC, Sherman KJ, Avins AL. A randomized trial comparing acupuncture, simulated acupuncture, and usual care for chronic low back pain. Arch Intern Med. 2009;169(9):858-866 [
abstract here].