Somatotopic Organization and Intensity Dependence in Driving Distinct NPY-Expressing Sympathetic Pathways by Electroacupuncture

Abstract

The neuroanatomical basis behind acupuncture practice is still poorly understood. Here, we used intersectional genetic strategy to ablate NPY⁺ noradrenergic neurons and/or adrenal chromaffin cells. Using endotoxin-induced systemic inflammation as a model, we found that electroacupuncture stimulation (ES) drives sympathetic pathways in somatotopy- and intensity-dependent manners. Low-intensity ES at hindlimb regions drives the vagal-adrenal axis, producing anti-inflammatory effects that depend on NPY⁺ adrenal chromaffin cells. High-intensity ES at the abdomen activates NPY⁺ splenic noradrenergic neurons via the spinal-sympathetic axis; these neurons engage incoherent feedforward regulatory loops via activation of distinct adrenergic receptors (ARs), and their ES-evoked activation produces either anti- or pro-inflammatory effects due to disease-state-dependent changes in AR profiles. The revelation of somatotopic organization and intensity dependency in driving distinct autonomic pathways could form a road map for optimizing stimulation parameters to improve both efficacy and safety in using acupuncture as a therapeutic modality.

Keywords: ST25 and ST36 acupoints; adrenal chromaffin cells; adrenergic receptors; electroacupuncture; neuropeptide Y; somatosensory autonomic pathways; spleen; sympathetic neurons; systemic inflammation; vagal-adrenal axis.