Aims: Plastic changes of neurons in spinal cord after peripheral nerve injury remain to be elucidated. The aim of this research is to clarify plastic changes of neurons and pericellular synapses in lumbar spinal cord after sciatic nerve transection.Methods: Neurons and pericellular synapses in lumbar spinal cord of rats were analyzed 6 weeks after sciatic nerve transection. The axonal volume of cortical neurons was labeled with biotinylated dextran amine, the volume of motoneuron soma with Fluoro-Gold, cholinergic interneurons with vAchT, and pericellular synapses with vGlut1 and vAchT. They were respectively estimated in the transection and sham groups.Results: No significant differences were found in the both groups with respect to the axonal volume of cortical neurons. The transection group showed the significant decrease regarding the volume of motoneuron soma (34% decrease, p<0.05), the number of cholinergic interneurons (35% decrease, p<0.05), and pericellular synapses for motoneurons (vGlut1 95%・vAchT 63% decrease, p<0.001) compared to the sham group. With respect to pericellular synapses for cholinergic interneurons, the number of vGlut1-positive synapses was more (40% increase, p<0.01) in the transection group than in the sham group.Conclusions: The number of cholinergic interneurons was decreased and the pericellular synapses for cholinergic interneurons were increased in the transection group. These responses appeared to be a complementary phenomenon to the loss of motoneurons and cholinergic interneurons. We would like to further investigate these influences after nerve repair.