[Morphological study on commonly-used acupoints for thyroid surgery under acupuncture anesthesia]

To study the morphologic structure, afferent projections of "Neiguan" (PC6), "Hegu" (LI 4) and "Futu" (LI 18) acupoint regions so as to understand their underlying mechanisms in acupuncture anesthesia for thyroid surgery.

A total of 66 Wistar rats were used in the present study. (1) Horseradish peroxidase (HRP, 10%, 10 microL) was injected into PC 6, LI 4 and LI 18 acupoints and the thyroid area on the right side, respectively (n = 6). (2) Propidium iodide (PI, 10% 10 microL) or Bisbenzimide (Bb, 5%, 10 microL) was injected into above-mentioned 3 acupoints and the thyroid region on the right side, respectively (n = 6). The numbers and percentages of the labeled neurons in the dorsal root ganglia (DRGs, C 1 - C 8 and T 1) were observed under microscope. (3) Cutaneous connexin (Cx) 43 immunoactivity of LI 18, PC 6, LI 4 and "Zusanli" (ST 36) regions and their individual non-acupoint regions (about 0.5 cm lateral to LI 18, PC 6, LI 4, and ST 36, n = 12) was determined by immunohistochemistry.

1) HRP-labeled neurons after injection of HRP into LI 18 were found in DRGs of C 1 - C 5, predominantly C 2 - C 4, those from LI 4 found in DRGs of C 3 - C 8. mainly C 5 - C 7, those from PC 6 found in DRGs of C 3 -T 1, chiefly C 5 - C 8, and those from the thyroid region found in C 1 - C 6, predominantly C 2 - C 5, suggesting an overlap or convergence of afferent projections from the 3 acupoints and the thyroid regions being in C 3 - C 5. 2) After injection of PI into LI 18, LI 4 and PC 6. and Bb into the thyroid region, the percentages of PI- and Bb-labelted neurons in DRGs of C 1 - C 8 and T 1 were from 46.4% to 50.0% and the percentages of the double labeled neurons were 3.8% in the LI 18-thyroid group, 3.1% in the LI 4-thyroid group and 3.6% in the PC 6-thyroid group, respectively, suggesting a bifurcate innervation of DRG neurons between theseacupoints and the thyroid region. 3) In comparison with the individual non-acupuncture and non-acupoint subgroups, the immunoactivity of cutaneous Cx 43 in the LI 18, LI 4, PC 6, and ST 36 subgroups was upregulated considerably after acupuncture stimulation (P < 0.05).

Neurons of DRGs of C 1-C 8 and T 1 innervating "Futu" (Ll 18), "Hegu" (LI 4) and "Neiguan" (PC 6) and the thyroid gland have an overlap or convergence in DRGs of C 3 - C 5 and a bifurcate innervation. Acupuncture stimulation may upregulate cutaneous Cx 43 expression in the acupoint regions.