Peripheral and Spinal Mechanisms of Acupoint Sensitization Phenomenon

Abstract

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.

Changes in Responses of Neurons in Spinal and Medullary Subnucleus Reticularis Dorsalis to Acupoint Stimulation in Rats with Visceral Hyperalgesia

“…The size and function of acupoints will vary along with the state of viscera. The so-called acupoint sensitization phenomenon is the specific reflection of visceral diseases through acupoints [ 21 , 22 ].…”

“…Many morphological studies observed the neuronal projections between spinal cord and SRD area [ 16 – 20 ], suggesting the existence of a neuronal circuit interconnecting the spinal cord and the medulla oblongata. In our previous studies [ 21 , 22 ], we observed that visceral inflammation could facilitate the responses of WDR and SRD neurons to acupoint stimulation and a linear relationship existed between the intensity of nociceptive stimulation to inner organs and the sensitivity of related acupoint. These findings suggest that the function of viscerosomatic convergence-facilitation at the spinal and medulla levels maybe related to acupoint sensitization phenomenon.…”

Detection of peripheral and central sensitisation at acupoints in patients with unilateral shoulder pain in Beijing: a cross-sectional matched case–control study

“…At some acupoints there appeared to be hypersensitivity towards temperature (heat sensitisation) or pain threshold (pain-sensitisation) under visceral pain. 9 25 But unlike those studies, we examined acupoints in patients with musculoskeletal pain in this study.…”

“…Many studies have observed that visceral lesions result in changed pain perception of some particular acupoints on the body surface. 9 Ben et al assessed the phenomenon of experimental pain-sensitive points in patients with gastric ulcer or gastritis and found that some acupoints were more sensitive than other areas. 10 Nevertheless, whether acupoints are more sensitive in patients with musculoskeletal pain has not been described in detail in previous studies.…”

What is the Acupoint? A preliminary review of Acupoints

“…Researchers have used animal models to explore mechanisms of pain sensitization. It is found that acupoints may be sensitized by visceral noxious stimuli and the sensitive degree of acupoints changed according to malfunction of internal organs . Myofascial trigger points (MTrPs) were proposed as a mechanism to explain musculoskeletal pain , and they may resemble acupoints in location and function.…”