Objective To investigate neuroanatomical characteristics of the primary sensory afferent and the motor neurons coming from and innervating acupoint "Chengshan"(BL 57) area in the rat by using cholera toxin subunit B conjugated with Alexa Fluor 488(CTB-Alexa488)

a new generation of fluorescent neural tracing reagent.Methods Four male SD rats were used in the present study.Under anesthesia

0.05% CTB-Alexa488(5μL) was injected into the central part of the rear of the hind leg

a corresponding site of "Chengshan"(BL 57) in the human body.After 40

4

8 surviving hours

the rat's brain

spinal cord and dorsal root ganglia(DRGs) of the lumbar segments(L1-L6) were dissected following perfusion with 4% paraformaldehyde

cut into sections and observed under fluorescent microscope equipped with a digital camera.The neurons labeled by CTB-Alexa488 were counted.Results All CTB-Alexa488 labeled neurons appeared in green under fluorescent filters of 45048 surviving hours

the rat's brain

spinal cord and dorsal root ganglia(DRGs) of the lumbar segments(L1-L6) were dissected following perfusion with 4% paraformaldehyde

cut into sections and observed under fluorescent microscope equipped with a digital camera.The neurons labeled by CTB-Alexa488 were counted.Results All CTB-Alexa488 labeled neurons appeared in green under fluorescent filters of 450

4

90 and were located ipsilaterally on the injection side.The labeled primary sensory neurons were found in the DRGs at L4(11 neurons) and L5(35 neurons).Among them

29 neurons(63.04%) were bigger

with their cell body diameters being 35490 and were located ipsilaterally on the injection side.The labeled primary sensory neurons were found in the DRGs at L4(11 neurons) and L5(35 neurons).Among them

29 neurons(63.04%) were bigger

with their cell body diameters being 35

5

0μm and 17(36.96%) smaller

with their body diameters being lower than 35μm.The labeled motor neurons were found to distri-bute in the mediolateral portion of lamina Ⅸ

forming a longitudinal column from L4 to L5.Of the observed 316 motor neurons

259(81.96%) belong to α type with their body diameters being 2550μm and 17(36.96%) smaller

with their body diameters being lower than 35μm.The labeled motor neurons were found to distri-bute in the mediolateral portion of lamina Ⅸ

forming a longitudinal column from L4 to L5.Of the observed 316 motor neurons

259(81.96%) belong to α type with their body diameters being 25

4

0μm and 57(18.04%) to γ type with their body diameters bei-ng lower than 25μm.Conclusion The CTB-Alexa488-labeled primary sensory and motor neurons innervating acupoint "Chengshan"(BL57) distribute in the DRGs of L4-L5.The present fluorescent tracing technique may be quite useful for investigating the neural characteristics of acupoints.