Objective To study the impact of insulin-like growth factor 1 (IGF-1) on the neural stem cell proliferation of the subventricular zone (SVZ) induced by transient forebrain ischemia in postnatal day 7 rats.Methods A total of 64 postnatal day 7 Sparuge-Dawley rats were randomly divided into ischemia group (EM>n /EM>=24), sham group(EM>n /EM>=24), ischemia plus antagonist group (EM>n /EM>=8) and ischemia plus saline group EM>(n/EM> =8). The cell proliferation and IGF-1 in the SVZ of the ischemia group and the sham group were observed 1, 4 or 7 days after ischemia with immunohistochemical staining. The cell proliferation and IGF-1 in the SVZ of the ischemia plus antagonist group and the ischemia plus saline group were detected after 7 days of continuous treatment with JB1 or without JB1 treatment.Results The number of BrdU+ cells and IGF-1+ cells of the ischemia group were significantly increased in the SVZ 1, 4, and 7 days after ischemia compared with that of the sham group (EM>P /EM>0.05). After the administration of JB1, the IGF-1 expression was blocked. The IGF-1+ cells were absent in ischemia plus antagonist group, while the IGF-1 expressed normally in ischemia plus saline group. The number of BrdU+ cells in the ischemia plus antagonist was sharply decreased compared with the ischemia plus saline group EM>(P/EM> 0.05) in the SVZ 7 days after ischemia.Conclusion Ischemia/perfusion up-regulates the expression of IGF-1 in neonatal rats, which may promote the proliferation of neural stem cells. Decrease of the neural stem cells proliferation dramatically after the administration of JB1 suggests that IGF-1 may play a key role on recovery of tr