RESUMEN
OBJECTIVE: To observe the peripheral and central neural connection of acupoint "Hegu" (LI4), "Neiguan" (PC6), "Futu" (LI18) and the thyroid gland (TG) region with fluorescence double-labelling method. METHODS: Thirty male Wistar rats were divided into LI4-LI18 group, PC6-LI18 group, TG-LI 18 group, LI 4-TG group, and PC 6-TG group, with 6 rats in each. Fluorescence dyes Propidium Iodide (PI, 10 microL) and Bisbenzimide (Bb, 10 microL) were, separately, injected into those acupoints mentioned above and the TG region. Sixty hours after PI-injection and 12 hours after Bb-injection, the rats under deep anesthesia were transcardiacally perfused with PBS containing 4% polyoxymethylene, followed by taking the spinal cord and dorsal root ganglia (DRGs) of the cervical segments (C1-C8) and thoracic 1 (T1) segment. Fluorescent single- and dual-labeled cells of the sliced DRGs and cervical spinal cord were observed by fluorescence microscope. RESULTS: (1) All PI- and Bb-labeled cells were found to distribute in DRGs from C1-T1 segments. PI single-labeled cells from LI4 and PC6 mainly distributed in DRGs from C4 to C8. Bb single-labeled cells from LI18 and TG region distributed in DRGs from C1-C6. (2) Dual-labeled cells in the LI 4-LI 188 group, PC6-LI18 group, LI4-TG group, and PC6-TG group distributed in DRGs from C3 to C7, suggesting bifurcate peripheral processes of the cervical DRG neurons to innervate LI8, LI4, PC6 and the TG region. And the dual-labeled cells of the TG-LI 18 group distributed mainly in DRGs from C1 to C4. (3) A small number of single-labeled neurons(about 8% of total labeled cells in DRGs) and only several dual-labeled neurons were found in the anterior horn of the cervical spinal cord. CONCLUSION: LI18, LI4 and PC6 and the thyroid gland have the same peripheral cells in DRGs of C3-C7 segments, suggesting that the bifurcate peripheral innervation may provide an anatomic evidence for the analgesic effect of acupuncture of LI18, LI4 and PC6 on thyroidectomy.