Neuroanatomical Basis for Acupuncture Point Pc8 in the Rat: Neural Tracing Study with Cholera Toxin Subunit B

Objectives This study was performed to investigate the innervations related to acupuncture point PC8 in rats using a neural tracing technique. Methods After 6 μL of 1% cholera toxin subunit B (CTB) was injected into the site between the second and third metacarpal bone in rats, a corresponding site to acupuncture point PC8 in the human body, CTB labelling was examined with immunofluorescence and immunohistochemistry in the dorsal root ganglia (DRG), spinal cord and brainstem. Results All CTB labelling appeared on the ipsilateral side of the injection. The labelled sensory neurons distributed from cervical (C) 6 to thoracic (T) 1 DRG, while the labelled motor neurons were located on the dorsolateral part of the spinal ventral horn ranging from the C 6 to T 1 segments. In addition, the transganglionically-labelled axonal terminals were found to be dense in the medial part of laminae 3–4 from C 6 to the T 1 spinal dorsal horn, as far as in the cuneate nucleus. Conclusions These results indicate that sensory and motor neurons associated with PC8 distribute in a distinct segmental pattern. The sensory information from PC8 could be transganglionically transported to the spinal dorsal horn and cuneate nucleus.