Objective    To investigate the effect of calcitonin gene-related peptide (CGRP) on early-stage bone fracture healing and on the expression of bone morphogenetic protein-2 (BMP-2) in bone tissue of rats.     Methods    Totally 30 SD rats with tibial fracture were randomly and equally divided into 3 group and received normal saline (control group)

CGRP or CGRP receptor antagonist injection intraperitoneally. In 1

2 and 4 weeks later

the fracture sites from the 3 groups were subjected to X-ray scanning

callus measurement and HE staining. The expression of the BMP-2 was detected by immunohistochemical method.     Results    There was no obvious difference on callus amounts among the 3 groups

but at 2 weeks after treatment

there were significantly more callus in CGRP group with enlargement in the fracture site than in the other 2 groups; The enlargement of CGRP group became minimized with fused cortex and almost normal morphology and size. So were the other 2 groups. Immunohistochemical results showed that exogenous CGRP significantly increased BMP-2 expression

but the expression was decreased significantly after administration of CGRP receptor antagonist.     Conclusion    Our results suggest that CGRP may participate in the regulation of bone fracture healing

and induce BMP-2 production

implying that BMP-2 may be related functionally with CGRP in the mechanism of bone metabolism.