Less hippocampal neuronal death in young gerbils following transient global cerebral ischemia is associated with long-term maintenance of insulin-like growth factor 1 and its receptors in the hippocampal CA1 region

Insulin-like growth factor 1 (IGF-1) is a well-known growth factor with well-defined neuroprotective effects against cerebral ischemia. However, the age-dependent differences in the expression of IGF-1 and its receptor (IGF-1R) in the brain following transient cerebral ischemia (TCI) have not been elucidated. In the present study, the differences in IGF-1 and IGF-1R in the gerbil hippocampal CA1 region of young and adult gerbils 5 min following TCI were determined. Seven days following TCI, the neuronal death in the hippocampal CA1 region of young gerbils was significantly less than that observed in adult gerbils. In addition, the immunoreactivity, and levels of IGF-1 and IGF-1R in the CA1 region of the normal young were higher than those in the normal adult. Four days following TCI, the immunoreactivity, and protein levels of IGF-1 and IGF-1R were markedly decreased in the adult group. By contrast, in the young group, the immunoreactivity and expression levels were much greater than those in the adult group. However, 7 days following TCI, all immunoreactivity and expression levels were markedly decreased when compared with those in the normal adult and young groups. In addition, the immunoreactivity and expression levels in the young groups were significantly higher than those of the adult groups. In conclusion, the present study demonstrated that the higher and sustained expression of IGF-1 and IGF-1R in the young gerbil hippocampal CA1 region following TCI may be associated with the reduced neuronal death compared to that in the adults.