Though this study is 5 years old, there hasn’t been much follow-up on what was discovered: “Some individuals with fibromyalgia may have a down-regulation or decrease in opioid receptor activity that may exaggerate pain sensitivity”
Previous studies indicate that fibromyalgia patients have increased sensitivity to temperature, touch, and pressure.
Moreover, some of Dr. Harris’s previous work demonstrated that people with fibromyalgia produce an increased amount of endogenous opioid peptides (also known as endorphins that naturally relieve pain) that act on the brain’s μ-opioid receptors to “naturally” reduce pain.
Other work by this same group showed that the fibromyalgia brain displays an enhanced response to painful stimuli, suggesting a problem with pain processing.
This current study sought to determine if these two factors, altered function of μ-opioid receptors and enhanced brain response to pain, actually occur simultaneously within the same group of people with fibromyalgia – and within the same brain regions
The study revealed a strong negative association between the brain’s response to pain and the binding availability of μ-opioid receptors:
the lower the receptor binding availability
the greater the brain’s response to pain.
For the first time, this study shows that μ-opioid receptor binding is tightly associated with the brain’s response to pain in fibromyalgia.
The data leads researchers to speculate that some individuals with fibromyalgia may have a down-regulation or decrease in opioid receptor activity that may exaggerate pain sensitivity.
Moreover, these same individuals are likely to not benefit from opioid medications as they may have fewer functioning receptors.
We find strong longitudinal associations between evoked pain activations suggestive of hyperalgesia, and µ-opioid receptor availability (binding potential, BP) within the same brain regions, in individual FM patients.
Positive associations were also observed between BOLD responses, and μ-opioid receptor BP (in opposite directions) with respect to clinical pain.
These data suggest that the µ-opioid system is somehow involved in the pathogenesis of FM, and may even help explain why these patients are generally not felt to respond to narcotic analgesics, and may even be made worse when these drugs are used therapeutically.