Objective: To compare the effect of different cervical and thoracic dorsal roots in conveying signals from electroacupuncture (EA) of acupoints of Pericardium and Sanjiao Channels to the spinal cord for analyzing the relative specificity of connection between PC and the heart.

Methods: Experiments were conducted on 85 Wistar rats anesthetized with chloralose (5mg/100g body weight) and urethane (42mg/100mg). After laminectomy, the cervical and thoracic segments of the spinal cord were exposed. Undermicroscopic observation, the fine nerve filament of the proximal end of the dorsal root was isolated after carefully tearing the spinal pia mater, and attached to the recording electrode. The reference electrode was placed beneath the skin of the incision. Two caudal and two rostra1 dorsal roots near the recorded dorsal root were cut off separately. Electrical activity of the fine nerve filament was observed and analyzed by using VC-l0 Memory Oscilloscope and histogramer. "Daling (PC 7) -Jianshi (PC 5) ", Quze (PC 3) of the Pericardium Channel (PC), "Yangchi (SJ 4) –Zhigou (SJ 6) ", "Tianjing (SJ 10) -Qinglengyuan (SJ 11) " of the Sanjiao Channel (SJ) were chosen and stimulated electrically with 1 and 2mA, frequency of 40Hz and intermittent waves.

Results: (l) Effect of EA of PC acupoints on the firing of nerve filaments. The effect of EA of PC acupoints on the electrical activity was observed in 60 nerve filaments of C5-8 and T1 dorsal roots. After EA stimulation of "Daling (PC 7) - Jianshi (PC 5), 3 of 12 C5, 5 of l2 C6, 7 of l3 C7, 3 of 12 C8 and 2 of 11 T1 nerve filaments increased considerably in the firing rate. After EA stirnulation of "Quze (PC 3), 3 C5, 4 C6, 6 C7, 3 C8 and 3 T1 of each 10 nerve filaments increased significantly in the firing rate. It indicates that C7 dorsal root plays the first important role in conveying EA signals from PC acupoints to the spinal cord and higher central nerve system; (2) Effect of EA of SJ Channel acupoints on the firing of nerve filaments After EA "Yangchi (SJ 4) –Zhigou (SJ 6) ", 2 of l0 C5, 7 of l0 C6, 5 of 10 C7, 1 of 10 C8, 2 Of
　　13 T1 nerve filaments increased significantly in the firing rate. After EA "Tianjing (SJ l0) -Qinglengyuan (SJ 11) ", 2 C5, 3 C6, 4 C7, l C8 and 1 T1 of each 10 nerve filaments increased strikingly in the discharge rate. It showed that EA signals of Sanjiao Channel acupoints transmitted to the spinal cord mainly by Way of C6 and C7 dorsal roots. Most of the above-mentioned nerve filaments responding obviously to EA stimulation were low-threshold nerve fibers. 18 of 20 filaments in "Daling - Jianshi" group and 15 of 17 filaments in "Yangchi- Zhigou" group responded considerably to touch or slightly clamp the skin in the receptive field. Only 1 of 20 filaments (C7) in "Daling - Jianshi" group and 2 of 17 filaments (C7 and C8) in "Yangchi- Zhigou" group responded to pain stimulation within the receptive field.

Conclusion: The periphery afferent pathway for transmitting signals from EA PC acupoints has its relative specificity.

By Liu Junling Gao yonghui & Chen Shuping.