Effects of Insulin Like Growth Factor-1 on the Abilities of Learning and Memory and Ultrastructural Changes in Hippocampus of Dementia Rats

Aim: To study the effects of insulin like growth factor-1(IGF-1) on the abilities of learning and memory and ultrastructural changes in hippocampus of dementia rats.Methods: Dementia rat models were established by transecting bilateral fornix-fimbria.Wistar male adult rats were divided into five groups: normal control group,sham group,dementia group,low dose IGF-1 group and large dose IGF-1 group.The dementia model rats received IGF-1(low dose IGF-1 group,large dose IGF-1 group) or saline(sham group,dementia group) by infused into the cerebroventricular space for 21 days after the operation.The normal control group accepted no treatment.The learning and memory abilities were measured by Morris water maze,and ultrastructural changes in hippocampus were observed under transmission electron microscopy.Results: Compared with the normal control group and the sham group,the dementia group showed the escape latency increased and the spanning platform times decreased,in which there were significant statistical differences(P0.01).Compared with the low dose IGF-1 group and the large dose IGF-1 group,the dementia group showed the escape latency decreased and the spanning platform times increased(P0.01).Compared with the large dose IGF-1 group,the low dose IGF-1 group showed the escape latency decreased and the spanning platform times increased(P0.01 or P0.05).Electron microscope of dementia group showed that most of neurons were intumesce and cavitative.Neuropil was cavitated too.Pro-and post-membrane were coalesce.Synaptic vesicles decreased.Electron microscope of the low dose IGF-1 group and the large dose IGF-1 group showed nuclear matrix cavitative lightly.Rough endoplasmic reticulum,chondriosome and lipofuscin could be observed in intracytoplasm.Some nerve plexus dissolved in axis cylinder.Conclusion: Transecting hippocampal fimbria-fornix can induce the damage of neuron in hippocampal and frontal lobe,and result in the learning and memory ability of rats decreased.IGF-1 can ameliorate the learning and memory abilities of the rats.