Peripheral and spinal mechanisms of acupoint sensitization phenomenon

This study was carried out on adult female Sprague-Dawley rats to observe the position, size, and sensitivity change of inflammatory reactions on body surfaces induced by colorectal import of inflammatory irritant mustard oil. Colorectal distension (CRD) was adopted as a visceral noxious stimulus to record the activities of spinal dorsal horn wide-dynamic range (WDR) neurons activities at spinal segments L1-L3. The study also observed the activations of WDR neurons by electro-acupuncture (EA) on acupoints of Zusanli-Shangjuxu before and after different intensities of CRD stimulation and the dose-response relationship between stimulus and response. The results show that in the case of visceral inflammation, the number of exudation points of neurogenic reaction on body surfaces increased along with the severity of visceral inflammation (Li et al. 2006). The area of peripheral receptive fields of WDR neurons also enlarged along with the intensity of visceral inflammatory response. The activation effect of EA on WDR neurons was positively correlated with the severity of visceral inflammation. Therefore, we concluded that the function of acupoints can be sensitized by visceral noxious stimuli. When the function of internal organs was damaged, the number of reaction points on body surfaces, the size of acupoints' receptive fields, and the sensitivity of acupoints changed accordingly.