| Backgrounds: In the spinal cord, motoneurons innervating the homonymous and synergistic muscles cluster into separately circumscribed longitudinal columns in ventral horn. Dendro-dendritic and dendro-somatic projections are common between these neurons. However, the function of this morphologic characteristic of motoneuron is not clear.Objectives: In this study, we attempted to study the characteristics of soma distribution and dendrite projection of LG and SOL motoneurons, and to clarify existence of synapses between dendrites and dendrites or dendrites and somas of spinal motoneurons, the related mechanisms, the properties of synaptic potentials, and possible functions of this synaptic connection. Finally, we adopted modeling analysis methods to compute the propagation of electrical synapse potential along the dendrite, influence of morphological and membrane electrical properties on this propagation, and spatial and temporal integration of electrical and chemical synapses in the modeled neuron.Results: 1) Both LG and SOL motoneuron pools locate in the dorsa-lateral of ventral horn in the cross section of the spinal cord, but along the longitude SOL pool distributes more caudally than LG pool. The peak distributions of motoneurons, which belong to different primary branches of LG nerve, appear in different longitude positions of the spinal cord, although the longitudinal ranges of distribution are much similar in these neurons. Both in the cross section and along the longitude of the spinal cord, there is little difference in distributions of motoneurons belonging to the same primary but different secondary LG nerve branches. 2) Wealthy dendrites are found in LG and SOL motoneurons, which extend along multiple directions in the ventral horn. Dense dendro-dendritic and dendro-somatic projections are evident between these neurons both in the cross and horizontal section of the spinal cord. 3) In adult rats, subthreshold stimulation (relative to the recorded motoneuron) of the...
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