Objective: To examine the effects of different sensitivities on the effectiveness of acupuncture analgesia by observing activation change characteristics of cerebral areas resulting from the influences of constitutions on analgesia effects and to discuss the response mechanism of central nervous system (CNS) to determine the factor of constitutions on acupuncture efficacy using cerebral functional magnetic resonance imaging arterial spin labeling (fMRI-ASL).
Methods: Participants with different sensitivities were assessed according to standard screening and grouped into two groups: insensitivity group (n＝24) and sensitivity group (n＝22). All participants were given acupuncture at the left-sided Zusanli point. Pressure pain threshold (PPT) of their body surface was determined before and after the acupuncture, and the two groups were subsequently compared in terms of analgesic effects and PPT rate of change; cerebral fMRI-ASL was performed; software such as SPM 8 and ASLtbx were utilized to preprocess the results, and correlation between regional cerebral blood flow (rCBF) and visual analog scale (VAS) score was determined using Pearson's correlational analysis.
Results: VAS score in the sensitivity group was significantly higher than that in the insensitivity group (P< 0.05); after acupuncture, PPT rate of change in the sensitivity group was higher than that in the insensitivity group (P< 0.05). The analyses revealed that there was a negative correlation between rCBF and VAS score for the right-sided anterior cingulate cortex in the insensitivity group and superior frontal gyrus in the sensitivity group (|r|>0.3 and P<0.05).
Conclusion: Different sensitivity to acupuncture is one of the crucial factors influencing analgesia effects. The sensitivity group had superior analgesia effect than the insensitivity group. Acupuncture might deactivate cerebral functional areas to generate analgesic effects.The superior frontal gyrus and bilateral anterior cingulate cortex, because of deactivation, play a positive role in sensitive patients, which is probably one of the CNS cerebral areas responding to acupuncture analgesia of people who are sensitive to acupuncture.
Keywords: Acupuncture analgesia; Arterial spin labeling technology; Cerebral functional magnetic resonance imaging; Constitution.