Ameliorative effects of angiotensin-IV on the expression of hippocampus synaptophysin and the cognitive function of diabetic rats

Cognitive impairment has been a common complication of diabetic. Recent evidences have pointed out angiotensin-IV (Ang-IV) can facilitate memory acquisition and recovery, whether it also can improve cognitive functions of diabetic rats with cognition disorder and the possible mechanisms if it really can are yet unknown. In this study, 45 Sprague Dawley (SD) male rats were divided into three groups randomly: control group, diabetic model group and diabetic model with Ang-IV treatment group. Their cognitive functions were evaluated through Morris water maze task; the synapses ultrastructure and relative mRNA concentrations and protein expression levels of synaptophysin in hippocampus were analysed and detected by transmission electron microscope, reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry and western blotting, respectively. Results show that, for Ang-IV treatment group, the cognitive functions were obviously improved, and the ultrastructure of synapses in hippocampus became more normalized, and the relative mRNA concentrations and protein levels of synaptophysin in hippocampus were also significantly increased, compared with DM. It is concluded that Ang-IV plays an important role in improving cognitive function of diabetic rats with cognition disorder, and the possible mechanisms are up-regulating the expression of synaptophysin and normalizing the ultrastructure of synapses in hippocampus.   Key words: Angiotensin-IV, synaptophysin, diabetes, cognition, hippocampus, rats.