Double-Blind Acupuncture Needle: A Potential Tool to Investigate the Nature of Pain and Pleasure

Background. Most of our knowledge about similarities in the neural processing of painful and pleasant sensations in the brain derives from studying each phenomenon separately. Patients often feel pain induced by acupuncture, which is noxious stimulation having the symbolic message of the cure, as pleasant. Objectives. We investigated whether the double-blind acupuncture needles are a potential tool to investigate coinciding pain and pleasant events. Methods. Participants were 109 healthy acupuncture students. An acupuncturist applied the double-blind placebo and the matching penetrating needle at bilateral forearm of each subject, one needle on each side of the arm. We asked the subjects to rate the pain associated with needle application and its unpleasantness or pleasantness on a visual analogue scale. Results. Of 65 penetrating needle applications that elicited pain, 29 (45%) subjects did not describe the pain as being unpleasant, and interestingly, 18 (28%) subjects described the needle insertion as pleasant. There was no significant difference in reported pain intensity between penetrating needles elicited pain that elicited a pleasant sensation and those that elicited an unpleasant sensation ( ). Conclusions. The double-blind acupuncture needles can be a potential tool for investigating the concomitant hedonic (pleasure) experience of pain. 1. Introduction Pain and pleasure have been considered opposites [1]. Most of our knowledge regarding pain and pleasure is obtained from independent studies of each phenomenon [1]. Needle insertion during acupuncture treatment which is one of the most popular complementary and alternative medicines is a noxious stimulation, but at the same time it gives patients an expectation of beneficial cure [2]. Very interestingly, patients who receive acupuncture treatment sometimes say that they feel pleasant having pain induced with acupuncture despite its invasive nature. The cause of this paradoxical phenomenon might be the effect of symbolic message of cure which had impact on the subjective utility of pain [1]. To the best of our knowledge, however, there has been no scientific study to show the relationship between pain associated with acupuncture needle insertion and its affective state under double-blind conditions. If it is scientifically confirmed that the penetration of an acupuncture needle can elicit both pain and pleasure concurrently, it can serve as a tool for investigating the neural mechanism for aversive stimuli that may have the subjective utility, which might close the gap between the pain and