Effects of push-pull action on memory function in rats

Abstract Objective : To investigate the effect of high G exposure on the memory function of rats after push-pull action . Method : 24 males

SD rats were randomly divided into control group, + 10 Gz group and the push-pull 3 groups, 8 rats. Changes in memory function of rats at different times after treatment were recorded. Results: Sliding avoidance test group the number of errors and the error time after exposure compared with the control group increased significantly [6 h respectively (3. 3 ± 1. 0), (2. 3 ± 0. 6) s, vs (0 0 ± 0. 0) , (0. 0 ± 0. 0) s ; 6 d are ( 0.3 ± 0.5) , (1. 3 ± 0.9) s , vs (0.3 ± ± 0. 5) , (0. 1 ± 0. 2) s , ( P < 0. 01) 〕 , also significantly increased compared with the + 10 Gz group ; the incubation period was significantly shorter than the control group after exposure ( P < 0.01 ) . Sliding accuracy group maze test is immediately after exposure (82. 5 ± 4. 6)% , 2 d is (75. 0 ± 16. 0)% , respectively, compared with the control group (92. 5 ± 4. 6 ) % , (100. 0 ± 0. 0) % is significantly lower (P < 0.01) . When the reaction is immediately after exposure (33. 6 ± 12. 9) s , 2 d is (67. 4 ± 32. 9) s , and with the control group compared to + 10 Gz group was significantly prolonged (P <0. 01) . Conclusion : + 10 Gz exposure for 3 min after push-pull action can lead to severe persistent memory dysfunction in rats.

Keywords : acceleration , push-pull action , push-pull effect , memory

In recent years, the data shows that due to the continuous improvement of the maneuverability of fighters and the need for aggressive actions in air combat , the push- pull maneuver (PPM) has an increasing chance of actual flight ( 1 ~ 3 ), which can lead to the pilot's + Gz endurance declines , and loss of consciousness is more likely to occur than pure + Gz . This phenomenon is called push-pull effect (PPE) . Since the 1990s , some fatal Class A flight accidents have been found to be related to the push-pull effect. This poses a serious threat to flight safety. Therefore , the push-pull effect has gradually been valued by people, and in recent years has become a new research hotspot in the field of aeromedical acceleration physiology. Previous studies have shown that high G- value exposure can cause cerebral ischemia and hypoxia in rats , which leads to a decrease in learning and memory ability . Push-pull operation can reduce the blood flow of cerebral blood after exposure to high G values . Therefore , learning The memory loss may be even worse , but the current changes in learning and memory function after push-pull action have not been reported. The aim of this study was to investigate the effect of high G- value exposure on memory function in rats after push-pull action .

1 objects and methods

1.1 Experimental animals and group 24 male SD rats (Experimental Animal Center of the University), body weight (185 ± 10) g, the reclaim for 1 week before the experiment and allowed to adapt to the environment, excluding shock, and other environmental factors in rats The effects of memory and behavior. The rats were randomly divided into control group, +10 Gz group and push group 3 groups of 8 animals.

1.2 Experimental methods

1.2.1 Animal exposure method The animal centrifuge was used to simulate + Gz with a radius of 2 m . The rat was fixed horizontally on the arm of the centrifuge , and the head of the rat was oriented toward the axis of rotation of the centrifuge. The push-pull group was exposed to -1 Gz for 1 min, followed by + 10 Gz exposure , and the peak action time was 3 min . + 10 Gz group only exposed for + 10 Gz , the peak action time was also 3 min, and the acceleration growth rate was 1 G · s- 1 . The control group was only placed in a plexiglass box for 3 min, but no + Gz exposure.

1.2.2 Avoiding dark experiment

It is learned that the rats stay in the bright box for more than 5 minutes . After the study, the number of errors, error time and latency of the rats were recorded within 5 minutes . The timing of learning and memory measurements is the same as the Y- type labyrinth experiment.

1.2.3 　 In the Y- type maze test , 9 times (90%) of the animals in 10 consecutive times were determined to be the standard of the society. 24 h after Exposure to + Gz, and to immediately after the end of exposure, 6 h, the changed 1 d, 2 d, 4 d and 6 d and accuracy required to accomplish this 10 reaction of rats were detected, per The test was carried out 10 times. Experiment time is 8 hours a day: 00 ~ 12: 00 (6 h exposure to 3 points in the afternoon of the day: 00 to 5:00), in the same under similar environmental conditions. 1.3 Statistical processing All data are expressed as mean ± standard deviation ,

Random unit group with " SPSS 10. 0 FOR WINDOWS "

Difference analysis , t test was used to compare the two groups .

2 results

2.1 avoidance rats change the number of errors, and time latency error experiments can be seen from Table 1, the number of errors and error control rats with baseline time increases measurement times as compared to no significant change; + 10 Gz the number of errors and the error time rats increased significantly compared to baseline values only in the exposed 6h (P <0. 01), compared to control group there was significant difference (P <0. 01); the number of errors sliding group of rats The error time was significantly higher than the baseline value at 6 h and 6 d after exposure (P < 0.01), and also significantly increased compared with the control group and the + 10 Gz group (P < 0.01) . No latency control rats compared to baseline values measured with increasing number of significant changes; + 10 Gz latency of rats did not change significantly after exposure, compared with the control group at all time points no significant differences; latency of rats in a push-pull The baseline values ​​were significantly shorter at 6 h , 2 d , 4 d, and 6 d after exposure (P < 0.01), which was significantly shorter than the control group and the + 10 Gz group (P < 0.01) .

2.2 The correct rate of the labyrinth experiment in each group and the change of the reaction time The correct rate of the control rats increased with the increase of the number of measurements and then increased (P<0.01); the rats in the 10 Gz group were correct. 2 d and immediately when the correct sliding of rats exposed group; rate immediately after exposure when the value of 2 d was significantly decreased compared to baseline (P <0. 01), at each time point compared with control rats significant differences were not The baseline value was significantly lower (P < 0.01), which was also significantly lower than that of the control group (P < 0.01) . The rats in the control group gradually decreased with the increase of the number of measurements compared with the basal value (P<0.01); the rats in the 10 Gz group reacted after the exposure.

Compared to baseline values and significantly prolonged engraved 2 d (P <0. 05) , significantly longer than the control group (P <0. 01); Immediately after rats exposed to push the reaction, when compared with baseline and 4 d 2 d The values ​​were significantly prolonged (P < 0.05) and significantly longer than the control group and the + 10 Gz group (P < 0.05, P < 0.01,) .

3 discussion

In recent years , fighters have been increasing their push-pull action during maneuvering. According to reports, the United States from 1982 to 1996 plane crash and death of people or the severe G - LOC accidents, there is a big possibility the top 12 accident sliding movement of 5% and 29% had possible push-pull action, stunt pilot experienced G -. The LOC have 47% is clearly related to the push-pull effect. In the past, people considered - Gz 's low endurance , there is no special anti-load equipment on the aircraft , so the pilot should be asked to avoid doing - Gz action. Modern tactics require fighters to attack each other with rapid action , and in order to reduce the chance of radar discovery , push-pull actions often occur in actual flight. Learning and memory are important brain functions essential for animals and human beings to survive . They are interrelated neural processes and external manifestations of nervous system activities , which can reflect the functional state of the nervous system. For humans, it is also the basis for intellectual activity, learning refers to the new behavior (experience) acquisition and development, and to maintain and reproduce the experience acquired through learning, which is the memory. The Y- maze experiment is a method for detecting the ability of the visual and spatial position of rats to judge and recognize. The experimental results show that, + 10 Gz group rats exposed than the control group was significantly longer reaction time and immediately after 2 d, and at other points of time and the control group before their exposure as compared to no significant difference. From + Start time 1 d after Gz exposure, sliding rats effects than + 10 Gz group and control group was significantly longer, and the correct rate than + 10 Gz group and the control group was significantly decreased, has not been restored to normal until 4 d, the It is suggested that the + 10 Gz exposure for 3 min after the push-pull action will significantly reduce the memory capacity of the rats , which is 2 d .

The reduction is most significant.

In the dark-avoidance experiment , the number of errors and the error time of the push-pull group were significantly increased at 6 h and 6 d after exposure compared with the control group and the + 10 Gz group . The incubation period was 6 h , 2 d , 4 d and 6 d after exposure. when compared with the control group and + 10 Gz significantly shortened; + the number of errors and the set of rats 10 Gz only error time than the control group increased significantly after 6 h exposure, there is no significant difference in latency compared with the control group. This indicates that the push-pull effect aggravates the effect of + Gz exposure on memory function in rats. Centrifuge test confirmed that a large number of push-pull operation can thereafter decreased endurance + Gz, slow heart rate, arterial blood pressure, impedance base, and total peripheral resistance decreased reflection adjustment, increasing stroke volume and the like. Analysis of the reasons, probably in - when 1 Gz, the inertia of blood to the head shift, a sharp rise in blood pressure caused by carotid artery carotid sinus and aortic arch baroreceptor reflex strong, the cardiac vagal activity increased central sympathetic central inhibition The heartbeat is slowed down , the cardiac output is greatly reduced , and the total peripheral resistance is reduced , resulting in a decrease in heart level blood pressure. - After the end of 1 Gz , the above effects do not fade immediately , so when the effect of + 10 Gz is followed , the head level blood pressure ratio is not pre-predicted.

First - 1 Gz is more severely reduced. At the same time, because the central activity of the heart is still strong , the sympathetic center is still in a state of inhibition , and the baroreceptor of the carotid sinus area is affected by the reflex response of hypotension at this time. - 1 Gz not only the head followed by + 10 Gz levels of blood pressure decreased more, but also damages the body's compensatory response of + Gz, resulting in + restore cardiovascular function than when 10 Gz - significantly deteriorated when 1 Gz, so that Ischemia and hypoxia in rat brain tissue is more serious , and even leads to ischemic changes of brain tissue neurons.

In conclusion , this study showed that + 10 Gz exposure for 3 min can cause transient memory dysfunction in rats , and + 10 Gz exposure for 3 min after push-pull action causes persistent and severe memory dysfunction in rats , indicating push-pull effect. The effect of + Gz exposure on memory function in rats was aggravated .