Acupuncture: Multimodal Enhancement of Colonic Motility by at ST36 is Mediated by TRPV1+ Cutaneous Sensory Fibers.
-
This study looked at how acupuncture improves gut movement, focusing on a specific nerve receptor called TRPV1 at the acupuncture point ST36 (Zusanli). I had a section in my book on Zusanli, and blogged about it here
-
Researchers used mice and applied electrical, manual, heat, and capsaicin stimulation at ST36.
-
All types of stimulation significantly increased colon movement, measured by stronger and more frequent contractions.
-
TRPV1-positive nerve fibers were mainly small sensory pain fibers, not motor or sympathetic nerves.
-
Using optogenetics, activating TRPV1 nerves alone mimicked acupuncture effects on the colon.
-
Silencing these TRPV1 nerves completely blocked acupuncture’s effect, proving they are essential for gut motility benefits.
Abstract
Background Acupuncture: Acupuncture has been shown to promote gastrointestinal motility. This study explores whether cutaneous transient receptor potential vanilloid 1 (TRPV1)+ fibers at Zusanli (ST36) acupoint can mediate the multimodal effects of acupuncture on colorectal motility, as well as examining their mechanistic role.
Methods: C57BL/6 mice were subjected to electroacupuncture (EA), manual acupuncture (MA), 46 °C thermal stimulation, and 1% capsaicin at the ST36 acupoint. Colon motility was quantified via the area under the curve (AUC) and contraction amplitude. Immunofluorescent co-localization of TRPV1 with CGRP, NF200, peripherin, and tyrosine hydroxylase (TH) was conducted in TrpV1Cre mice to determine neural phenotypic subtypes. Furthermore, TrpV1ChR2-eYFP and TrpV1NpHR-eYFP transgenic mice that underwent optogenetic activation or silencing of local TRPV1+ fibers at ST36 were evaluated for acupuncture-like stimulation effects on colorectal AUC and amplitude.
Results: All applied stimuli in C57BL/6 mice significantly increased colorectal motility parameters (AUC and amplitude, p < 0.05) compared to baseline. TRPV1+ somatosensory neurons in the dorsal root ganglion (DRG) predominantly co-expressed with peripherin (46.76%) and CGRP (27%), which are markers of unmyelinated peptidergic fibers, but rarely with NF200 (6%) or TH (< 1%). Optogenetic activation (30 mW blue light) of TRPV1+ fibers in TrpV1ChR2-eYFP mice mimicked acupuncture-like stimuli, with significantly enhanced colorectal AUC and amplitude (p < 0.05). In contrast, optogenetic silencing of TRPV1+ fibers with yellow light abolished acupuncture-like stimulation of colorectal motility in TrpV1NpHR-eYFP mice (p < 0.05).
Conclusion: Through the use of spatiotemporally precise optogenetic control, our study revealed that TRPV1+ sensory fibers at ST36 are the major convergent pathway for multimodal (electrical/mechanical/thermal/chemical) enhancement of colorectal motility by acupuncture.