OBJECTIVETo investigate the biochemical characteristic of the neurons associated Zusanli (ST 36) in the rat by using Alexa Fluor 594 conjugated cholera toxin subunit B (AF594-CTB) neural tracing and calcitonin gene-related peptide (CGRP) fluorescent immunohistochemical techniques.

METHODSFour male Sprague Dawley rats were injected with AF594-CTB into the corresponding area of the Zusanli in the human body. After 3 surviving days, the rat's spinal cord and dorsal root ganglia (DRGs) at lumbar segments were dissected following perfusion with 4% paraformaldehyde, cut into sections, and then stained with CGRPfluorescent immunohistochemical method.

RESULTSAF594-CTB labeled sensory neurons were detected in the L3-L6 DRGs with high concentration in L4 DRG, and the labeled motor neurons located in the dorsolateral and intermediate regions of lamina IX from L3-L5 segments with high concentration at L4. Meanwhile, CGRPpositive neural labeling distributed symmetrically on both sides of DRGs, anterior and dorsal horns of spinal cord. In the AF594-CTB labeled neurons, 37% sensory neurons and 100% motor neurons expressed CGRPpositive.

CONCLUSIONThese findings present the morphological evidence to demonstrate that the sensory and motor neurons associated Zusanli in the rat distributed with segmental and regional patterns, and contained CGRP-expression.