Objective To study the changes of agrin expression in spinal cord motor neurons after somaticautonomic ventral root (VR) anastomosis and somaticsomatic VR anastomosis, and the factors related to the synapse formation of foreign nerve regeneration. Methods Artifical somaticautomomic reflex pathway and somatic nerve selfanastomosis were established in rats. Retrograde tracing was carried out to label the motor neurons, and the neurons were isolated by flow cytometry. Realtime PCR was used to investigate the agrin mRNA expression of the neurons.Anterograde tracing and immunofluorescence technique were employed to label the new synapses of pelvic ganglia (PG). Results After 4 months of surgery, the somatic nerve can regenerate into PG successfully and form new synapses observed under laser scanning confocal microscope. The neurons involved in foreign nerve regeneration can be isolated successfully by retrograde tracing and flow cytometry.The expression of agrin in LSUB>4/SUB>-LSUB>6/SUB> VRs anastomosis group was lower than that of the control group of LSUB>4/SUB>-LSUB>4 /SUB>VR self-anastomosis (P<0.05) and the normal group (P<0.05).Conclusion The somatic nerve could regenerate into PG and form new synapses.The differences of agrin expression