Effects of chronic intermittent hypoxia on the cognitive function and neuron structure of hippocampus in mouse model of Parkinson's disease

Abstract

Objective To investigate the effects of chronic intermittent hypoxia (CIH) on the cognitive function, neuron structure and synaptophysin (Syn) expression of the hippocampus in mouse model of Parkinson's disease (PD). Methods A hypoxia⁃reoxygen device was used to prepare the model of CIH. Meanwhile, the PD mouse model was built by intraperitoneal injection of paraquat (PQ). The cognitive function was evaluated by Y⁃type electric maze and step-down test. Syn expression in the hippocampus was estimated by immunohistochemistry. The neuron structure in the hippocampus was observed by HE staining, Nissl staining and the electron microscope. Results Comparing to control group, a significant decrease was found in learning and memorizing performance (P < 0.05, for all) and the amount of neuron, while a significant increase was seen in total reaction time (TRT) and error reaction (ER) in Y-type electric maze and step-down test and the gray value of Syn in the hippocampus in PQ, CIH, and PQ + CIH groups. Various degrees of anomaly were observed in neuron structure of hippocampus by HE staining, Nissl staining and electron microscopy in PQ, CIH, and PQ + CIH groups, while presented most obviously in the latter group. Conclusion The PQ-induced impairment of cognitive function in PD model mice was aggravated by CIH, which may be related to the damage of neuron structure and the decrease of synaptic function in hippocampus.