Objective To study the temporo-spatial changing laws of calcitonin gene-related peptide(CGRP)in the rat model of sciatic nerve ligation.Methods Totally 48 Sprague-Dawley rats were randomly divided into sham-operation group(n=6)and experimental groups which survived for 1,3,5,7,14,21,28 d respectively after sciatic nerve ligation(n=6 at each time point).The distribution and quantity of CGRP in sciatic nerve,dorsal root ganglion(DRG)and spinal cord were detected by immunohistochemistry and image analysis methods.Results A large amount of CGRP piled up in the sciatic nerve at 1 d after the ligation,significantly higher in proximal segment than that in distal segment,gradually dropping till disappear basically at 14 d in proximal segment and at 7 d in distal segment.The expression of CGRP in DRG at 7 d began to drop after the ligation,at 21 d to the minimal value and at 28 d lower than normal.The CGRP-immunoreactivety in ipsilateral spinal dorsal horn at 14 d decreased after operation,but the immuno-positive areas of CGRP were of no changes.There are no changes in the CGRP-positive spinal ventral motoneurons of all groups.Conclusion The changes of CGRP presented a temporo-spatial pattern following peripheral nerve legation,maybe resulting from the deficiency of neurothrophins from target organs.