Diffuse Noxious Inhibitory Control (DNIC) of Le Bars: Literature review about the responsible neurological circuits of DNIC explains new additional characteristics about acupoints not included in the description of Le Bars.

 

Fossion J.P.J. 

Scientific Commission of the Belgian Association of Medical Acupuncture/ Brussels/ Belgium.

 

Introduction

Diffuse Noxious Inhibitory Control (DNIC) was described by Le Bars in ’89. Denial of topographic specificity of acupoints became an absolute dogma by his famous acupuncture experiment in ’91 referring to the “whole body” representation of wide dynamic range (WDR) neurons, as to its cutaneous, visceral and locomotor afference, and the subsequent irrelevance of localization of the needled point.

 

Aim

Does the DNIC on basis of heterotopic inhibition by its responsible subnucleus reticular dorsalis (SRD) explain other properties of acupoints beside topographic (a)specificity?

 

Methods

We made a review in literature research concerning studies about the SRD and WDR-neurons since Le Bars.

 

Results

Neuroscience literature points out that the subnucleus reticularis dorsalis (SRD) is responsable for the heterotopic segmental inhibition in DNIC, but is also responsable for homotopic facilitation of a receptive field, called prioritization (Almeida & Lima). Furthermore, there are two somatotopic representations of the face in the SRD and the WDR-neurons on multiple levels are somatotopically alligned. There is a description of the phenomenon of Wind-Up of WDR-neurons, not taken into account by Le Bars. (Wind-Up: temporal summation of partial depolarizations by previous or current pathology).

 

Conclusions

Our model of double contrast (heterotopic inhibition & homotopic prioritization) proposes following characteristics.

  1. SRD is a common substrate that could explain DNIC analgesia in somatic- as well as in ear acupuncture by heterotopic inhibition described by Le Bars.
  2. The SRD, increasing segmental contrast, could explain the Da Qi needling sensation through homotopic facilitation (prioritization) of the receptive field as described by Almeida & Lima.
  3. Since the SRD shows facial somatotopy, specificity of acupoints as defined by their precise localization regains credit, at least on facial level and for ear-acupuncture.
  4. The “whole body” representation in wide dynamic range (WDR) neurons only refers to its afference, not its efference through somatotopical allignment.
  5. We consider that there is sufficent evidence to refute the absoluteness by the Le Bars-exclusion of topographic specificity of acupoints. But we consider also that the topographic “specificity” of somatic acupoints, as described by Peter Deadman, respresents a “whole lot of body representation”, reminiscent of Le Bars, but not a “total” body representation.
  6. We postulate that the WDR-efferences activate a hybrid reticular interface in sensorimotor integration with anticipatory potentials of readiness.
  7. Le Bars explains why acupoints distant from a pain-site may be efficiënt (heterotopic). Almeida concludes that DNIC cannot explain analgesia of points near a lesion (so another system must coexist).
  8. Wind-Up can explain the allodynic property of all ear-points but in somatic acupuncture only Ah Shi points (electively tender by pressure) or Travell-points are explained. Therefore another system than DNIC must be searched for to explain the non-allodynic somatic acupoints.
  9. The needling sensation by manipulation of the needle (Da Qi) can be explained by recruitment of longitudinal preferential propriospinal synaptic connections, in terms of which “meridians” could be redefined.
  10. The phenomenon of “healing crisis” (immediate but short-lived exacerbation of main complaint) of trigeminal neuralgia and migraine in ear acupuncture can be explained by homotopic facilitation (prioritization) of Almeida-Lima.
  11. Paul Nogier described three phases of the same point (ectodermal-, endodermal- & mesodermal representation). Wind-Up of Wide Dynamic Range-neurons explains why the same ear-point may represent in principle all tissue origins. Question is if WDR-neurons might be differentiated in terms of acute-, degenerative- or chronic stages as suggested by Nogier.