Abstract: Abstract: Objective To map the specific distribution of the dendritic projections of the motor neurons related to the large intestine channel of hand-yangming and the pericardium channel of hand-jueyin in the spinal cord of rat. Method Cholera toxin B subunit combined with the horseradish peroxidase (CB-HRP) was injected as a neuronal tracer into the acupoints in the muscles and deep tissues of large intestine channel of hand-yangming and the pericardium channel of hand-jueyin. Each acupoint received an injection of 5 μL CB-HRP. Three to four days after injection, rats were perfused with fixatives and the cervical spinal cord was harvested, followed by TMB chemo-histological reactions to label the motor neurons. CB-HRP positive motor neurons?were observed with light microscope in the transverse and the horizontal sections.?Result?The motor neurons innervating the muscle groups related to each of the two given meridians (the large intestine channel of hand-yangming and the pericardium channel of hand-jueyin) formed a longitudinal?neural column?in the ventral horn of the cervical spinal cord.?Dense dendritic-dendritic and dendritic-soma projections were observed between the motor neurons within the same neural column. Conclusion?Our results indicated that the motor neurons related to a given meridian formed a longitudinal motor neuron column in the spinal cord ventral horn. The dendritic-dendritic and dendritic-somal projections?exclusively within the same motor neuron column corresponding to a certain meridian channel might be the morphological basis of meridian propagation as well as meridian reflex activities.?

Key words: Key words: Meridian, motor neuron dendritic projection, the large intestine channel of hand-yangming, the pericardium channel of hand-jueyin, CB-HRP.