Insulin-like growth factor-1 (IGF-1) has been demonstrated to have neuroprotective effects,but little is known concerning its role in vascular dementia (VaD).This study aimed to evaluate expression of IGF-1 signaling in hippocampus in rat model of VaD, and probe the underlying mechanisms.Permanent occlusion of bilateral common carotid arteries (2-VO) was used as VaD model.Learning and memory functions were declined significantly in 2-VO rats, and these impairments were further deteriorated with the prolongation of 2-VO treatment.IGF-1, IGF-1 receptor (IGF-1R),total Akt and phosphorylated Akt (p-Akt) were all measured at 1,2 and 4 months following 2-VO injury.Compared with controls, IGF-1, IGF-1 mRNA and p-Akt expression were significantly decreased in hippocampus of 2-VO rats.However, changes of IGF-1R and total Akt levels were not significant.These results suggest that down-regulation of IGF-1 and p-Akt may contribute to the impairments of learning and memory functions after 2-VO.IGF-1/IGF-1R signaling system may involved in the onset and development of VaD.