In Adjuvant-Induced Arthritic Rats, Acupuncture Analgesic Effects Are Histamine Dependent: Potential Reasons for Acupoint Preference in Clinical Practice

Figure 2

Interaction of histamine signal and pain sensation in case of itch suppression by pain and acupuncture analgesia. (a) In a pathological condition, pain suppresses the itch sensation. Mast cells are involved in the itch sensation in two possible ways: the activation of histamine receptors in a histamine-dependent fiber (red line) and the activation of PAR-2 by tryptase (green line). Both of these forms of activation are suppressed by the activation of pain (blue line) at the spinal level. (b) In the case of acupuncture, mast cells are activated by the mechanical force through the manipulation of the needle. The histamine release activated the histamine-dependent fiber through H1 receptors. Since the acupoint is away from the pain site, it is not interrupted by the activation of the pain sensation but activates the histamine target in the brain and initiates acupuncture analgesia.

(a) Suppression of itch by pain sensation in pathological

(b) Initiation of acupuncture-induced analgesia condition