Neural interconnection between acupoint 'Chéngshān' (承山BL57) and sciatic nerve in the rat

Objective The aim of this study is to assess the neural interconnection between the acupoint “Chengshān (承山BL57)” and sciatic nerve from the peripheral nervous system (PNS) to the central nervous system (CNS). Methods SD rats were systematically examined from the hip to the hind limb along the route of sciatic nerve with regional anatomical technique, and further traced from the BL57 and the trunk of sciatic nerve by the neural tracing technique with cholera toxin subunit B (CTB) and CTB conjugated Alexa Fluor 488 and 594 (CTB-AF488/594). Results After regional anatomy, it was found that the sciatic nerve ran down from the hip to the hind limb and sequentially sent out the tibial and sural branches respectively to the deep and superficial layers of BL57. The CTB labeling associated with both BL57 and sciatic nerve distributed in the same spinal segments and definite regions, including the sensory neurons in lumber 3 (L3) -lumber 6 (L6) dorsal root ganglia (DRGs), transganglionic axons mainly in the L3-L6 spinal dorsal horn, Clarke's nucleus, and gracile nucleus, as well as motor neurons mainly in the L3-L6 spinal ventral horn. However, the amount of neural labeling was significantly less in the cases of BL57 than that of sciatic nerve. Conclusions These results indicate that there is distinct sensory and motor interconnection between the BL57 and the sciatic nerve, which may potentially serve for the active role of the BL57 playing in meliorating the disorders of sciatic nerve.