Objective To study the peripheral and central neural involvements of acupoint "Taixi"(KI 3) by using Horseradish Peroxidase(HRP).Methods Ten male SD rats were used in the present study.5μL of 1% HRP was injected into the excavate site between the apex of medial malleolus and the Achilles tendon of the left hind foot

a corresponding site of acupoint "Taixi"(KI 3) in the human body.After 36 surviving hours

the rat's brain

spinal cord and dorsal root ganglia(DRG) of the lumbar segments(L) were dissected from the perfused experimental animals

and their tissue sections were examined with 3

3'

5

5'-tetramethyl-benzidine histochemistry for revealing HRP-labeling.Results All the HRP-labeling appeared ipsilaterally to the injection side.Numerous HRP-labeled neurons were detected in the DRGs of L4-L6 segments with their number being L5>L4>L6.A longitudinal column of HRP-labeled motoneurons was found in the dorsolateral and mediolateral portions of the spinal cord

distributing in the lamina Ⅸ from the caudal L4 to the rostral L6.Additionally

the transganglionic HRP-labeled central projection axonal terminals were found to be dense in the central part of laminae Ⅰ-Ⅱ from L4 to the rostral L6

and to scatter in the central part of gracile nucleus.Conclusion HRP-labeled primary afferent and efferent innervating acupoint "Taixi"(KI 3) are DRGs of L4-L6

the dorsolateral and mediolateral motoneuron columns of L4-L6

and the centrally projecting axonal terminals of laminae Ⅰ-Ⅱ of the spinal cord and the gracile nucleus.