Stimulation of
acupuncture point Pc6, located above the median nerve, has been shown to be effective in treating
nausea and
vomiting. It has also frequently been reported to cause a heart rate reduction. The mechanism behind this autonomic reaction has not been clarified, so far. We combined brainstem-sensitive functional magnetic resonance imaging with heart rate recording and time-resolved rating of the
needling sensation to measure neuronal correlates of sensations and autonomic reactions during acupuncture. On the cortical level,
needling sensation activated typical
pain-related areas, of which the ventromedial and dorsolateral prefrontal cortex and perigenual anterior cingulate cortex were further involved in mediating the heart rate response. In the brainstem,
needling sensation activated nuclei of the descending
pain control system, in which a network of hypothalamus, periaqueductal gray, rostral ventromedial medulla, and ventrolateral medulla was identified as the source of the heart rate changes. Our findings indicate that acupuncture may be a special
pain stimulus, whose autonomic concomitants could explain its non-
analgesic effects and in some cases even have a therapeutic potential.