Effect of Aβ_(1～40) on expression of synaptophysin and synaptic number of hippocampal neurons in rat after injection of β-amyloid protein 1-40 into hippocampus

[Objective] To observe effect of Aβ1～40 on expression of synaptophysin and synaptic number of hippocampal neurons in the rat after injection of β-amyloid protein 1-40 into hippocampus. [Methods] The animal model of AD was established after Aβ1～40 was injected into hippocampus. With the method of immunity histochemical staining coupled with computer image analysis system, observed the expression of synaptophysin in the rat hippocampal neurons. Ultrastructure and synaptic number in the hippocampus were observed by transmission electron microscope. [Results] Synaptophysin immuno-positive products were widely distributed in neuronal nuclei of hippocampus of sham operation groups rats. Compared with that of sham operation groups, synaptophysin immuno-positive products in the hippocampus CA2 sector neurons were decreased obviously (P 0.05) after injection of β-amyloid protein 1-40 into hippocampus. Expression of synaptophysin in the menstruum groups was the same as that in sham operation rats. In hippocampus of Alzheimer′s disease rats, mitochondria were swollen and deformed, endoplasmic reticulums were dilated, The number of axons and dentrites as well as synapses were decreased obviously (P 0.05). There was significant difference in synaptic number between Sham operation group and AD group. Synaptic number in the Menstruum groups was the same as that in sham operation rats. [Conclusion] β-amyloid protein may down-regulate the expression of synaptophysin in hippocampus neurons, and the synaptic number in the hippocampus of AD are decreased. They are presumed to be involved in the pathological processes of Alzheimer′s disease.