The Study On Hippocampal Injuries And Alterations Of Heart And Cerebral Vasculature In Mice After Chronic Cold Exposure

Stress response refers to organism’s reactions to external or internal environmental alterations. It is known that physiological functions should be carried out under constant body temperature. As an external stress factor, cold exposure can not only cause skin frostbite, but also hurt various systems, such as movement system, cardiovascular system, immune system and the nervous system as well, resulting in various diseases. Therefore, it is of great significance to understand the risks of cold exposure to people’s health. Generally, clinic doctors and research scientists have focused on certain diseases caused by cold exposure, such as some skin injuries, cardiovascular diseases, respiratory diseases and metabolic diseases. Study has demonstrated cold exposure could degrade humam cognitive performance, so we speculate that chronic cold exposure can also affect the central nervous system of mice. The hippocampus located in the temporal lobe is an important part of central nervous system, and plays an important role in the process of learning, memory and other physical processes. Based on the important physiological functions of hippocampus, we studied if chronic cold exposure could make hippocampus injure. In the processes of building model, we discussed the alterations of heart and cerebral vessels after chronic cold exposure in mice. So this research is divided into two parts that the first part was aimed to investigate the hippocampal stress injuries in mice after chronic cold exposure; the second part was tried to investigate the alterations of heart and cerebral vessels after chronic cold exposure in mice. Our data should contribute further knowledge in cryomedicine and new clinical treatment strategies. Furthermore, our data are also meaningful in areas such as military survival and athletic performance in extreme cold environments.Objective:(1) The present study was aimed to investigate the hippocampal stress injuries in mice after chronic cold exposure, and the pathological mechanisms were discussed as well.(2) The study was tried to investigate the alterations of heart and cerebral vessels after chronic cold exposure in mice. In the meantime, the pathological mechanisms were discussed as well.Methods: In the study, 60 adult male mice from 90 to 120 d were used and divided into control group and cold exposure group in random. Mice in cold exposure group were fed at temperature from-1 and ℃4 for 30 days to make the chronic cold exposure model. ℃ Mice in control group were fed at temperature from 20℃ and 25℃. Then, the chemiluminescence method was used to detect the serum estrogen levels, and stress injuries and neural immune cells were visualized with immunocytochemistry as well. Simultaneously, heart mass index was measured, and blood routine analyses were detected using blood cell analyzer. The histological structure of cardiomyocytes was visualized with hematoxylin-eosin(HE) staining, and the cerebral vasculature was visualized with ink perfusion assay.Results:(1) Chronic cold exposure could induce the oxidative stress reaction, inflammatory injury, neuroapoptosis in mouse hippocampal CA1 area(P<0.01). In the meantime, the neural immune cells and estrogen levels increased significantly(P<0.01).(2) Chronic cold exposure could induce myocardial hypertrophy and decrease the cerebral vascular density in mice. The number of white blood cells, lymphocytes, red blood cells and blood platelet increased, and estrogen level of blood increased as well, which may contribute to the pathological alterations of cardiovascular system.Conclusions:(1) Chronic cold exposure could induce various injuries, such as oxidative stress and neuroapoptosis, and the neural immune cells were involved in the reactions. In addition, the regulation of estrogen may play an important role in animal self-protection.(2) Chronic cold exposure could induce myocardial hypertrophy and the alterations of blood cells, cerebral vasculature and estrogen. The pathological alterations of blood cells, cerebral vasculature and estrogen may be involved in the production of myocardial hypertrophy.