Comparative effects of acupuncture in Japan and the United States on dental pain perception.

The effect of low frequency electrical acupunctural stimulation on the perception of induced dental pain were compared in two cultural settings. Twenty Japanese and 20 American subjects (consisting of 10 Caucasians and 10 second or third generation Japanese) were tested in two functionally identical laboratories, one at Tottori University in Yonago, Japan and the other at the University of Washington. Each subject underwent a control and an acupuncture session on separate days wtih subjects counterbalanced for carry-over order effects. Sensory decision theory (SDT) analysis demonstrated a significant reduction in perceptual capability and an increased bias against reporting stimuli as painful following the acupuncture as treatment which was performed bilaterally at traditional facial points. No significant differences between groups in alteration of perceptual capability, bias or pain threshold were demonstrated, indicating that the cultural and racial differences studied did not influence responses to acupuncture in a laboratory setting.

Event-related potential correlates of analgesia; comparison of fentanyl, acupuncture, and nitrous oxide.

This study was undertaken to determine whether different analgesic treatments result in a common change in the event-related potentials (ERP) elicited during painful dental stimulation. The effects of electrical acupuncture delivered at 2 Hz to LI-4, the opiate fentanyl 0.1 mg i.v., and the inhalation analgesia mixture of 33% nitrous oxide in oxygen were examined in volunteers undergoing painful tooth pulp stimulation. ERPs were recorded at vertex and subjects provided reports of pain intensity. Discriminant function analysis was used to determine which subset of the pain report and ERP variables could best discriminate baseline from treatment conditions without regard to specificity of treatment. Together with pain report, amplitude of the ERP positive deflection at 250 msec was a significant indicator of analgesia across the 3 treatments. Other changes specific to the individual treatments were also observed. Since the 250 msec amplitude measure was not redundant statistically with pain report, the ERP data provided significant new information about analgesia even though pain report was a very sensitive measure. Pain report alone could account for 48% of the variance across treatments while ERP measures alone accounted for 34%.

Evoked potential assessment of acupunctural analgesia: attempted reversal with naloxone.

The effects of electrical acupunctural stimulation (2 Hz) on pain judgments and evoked potentials are reported for two experiments using dental dolorimetry. In the first experiment subjects received acupuncture at points located in the same neurologic segment as the test tooth. In the second experiment subjects received acupuncture at points on the hands located on acupuncture meridians. In both instances acupuncture resulted in a reduction in pain intensity and smaller evoked potential amplitudes, but naloxone neither reversed the analgesia nor did it affect the evoked potentials. A pilot study was carried out to determine whether manual rather than electrical stimulation would produce an analgesia reversible by naloxone, but it failed to do so. These findings contribute to the growing evidence that acupunctural stimulation significantly reduces pain sensibility in volunteers undergoing dolorimetric testing, but they do not support the hypothesis that endorphin release is a mechanism by which acupuncture exerts analgesia.