調控脊髓基因對於針刺痛之影響(第三年)

Although induction of deep aching sensation, De-Qi, is generally accepted as a
standard acupunctural practice, whether an intense nociceptive stimulation is required
for optimal analgesic effect remains controversial. In freely moving rats we first
demonstrated that intramuscular injection of 100 μl 5% formalin, a noxious irritant, in
the Zusanli acupoint (ST-36) induced intense nociceptive behavior. Tail-flick latency
and c-fos expression were then compared among halothane-anesthetized rats receiving
either low-intensity electroacupuncture (10× threshold of local muscle contraction),
high-intensity (20× threshold) electroacupuncture (30 min, 4Hz), intramuscular formalin,
or normal saline injection at the right Zusanli acupoint. We found that formalin injection
at the acupoint markedly increased tail-flick latency and induced greater c-fos
expression at the superficial and deep laminae of spinal cord dorsal horn compared to
saline injection. Electroacupuncture prolonged the cumulative tail-flick latency in an
intensity-dependent manner but, in contrast to formalin, did not provide intensity
sufficient to induce c-fos expression throughout the 2nd to 5th lumbar segments. Our
data indicated that although noxious chemical stimulation at the acupoint can elicit
comparable analgesic effect, non-noxious electrical stimulations produce even greater
analgesic responses in an intensity-dependent manner. These findings suggest that
generation of intense aching sensation, De-Qi, is not required for the analgesic effect
provided by electroacupuncture.