Abstract Objective : To investigate the effect of high G exposure on the memory function of rats after push-pull action . Method: 24 male SD rats were randomly divided into control group, + 10Gz 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 , push- pull maneuver (PPM) has an increasing chance of actual flight ( 1 ~ 3 ) , which can lead to pilots. + Gz decreased endurance, more simple than + Gz role in the occurrence of loss of consciousness, a phenomenon called the push-pull effect (push - pull effect, PPE) [2, 3]. 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 [ 3, 4 ]. 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 indicated that exposure to high G values can cause cerebral ischemia, hypoxia, resulting in decreased learning and memory [5, 6], the value of the push-pull operation of the high G can thereafter exposed in cerebral blood flow decreased more even, therefore, it may also reduce the ability of learning and memory even more, but the change on learning and memory function after sliding motion has 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 grouping
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 the impact shock, and other environmental factors on memory and behavior in rats . 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 rotating 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 1G · s - 1 . The control group was only placed in a plexiglass box for 3 min, but no + Gz exposure.
1. 2. 2 Avoid dark experiment [ 7 ] Take the rats in the bright box for more than 5 minutes for learning. 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 measurement is the same as the Y- type labyrinth experiment.
1. 2. 3 　 The Y- type maze test [ 7 ] was determined to be the standard of the study in 9 times (90%) of the animals in 10 consecutive times . 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 analysis All data were expressed as mean ± standard deviation . The random unit group analysis of variance was performed using " SPSS 10. 0 FOR WINDOWS " , and the t test was used for comparison between the two groups .
2 results
2.1 avoidance rats experimental errors, error time and latency changes seen from Table 1, the number of errors and error control rats with baseline time increases the number of measurements compared to no significant change; + 10 Gz 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); push rats The number of errors and the time of error were significantly higher than the baseline values ​​at 6 h and 6 d after exposure (P < 0.01), and also significantly increased compared with the control and +10 Gz rats (P < 0.01) . No latency control rats compared to baseline values measured with increasing number of significant changes; + 10Gz latency of rats did not change significantly after exposure, compared with the control group at all time points no significant difference; latency in push-pull are exposed rats After 6 h , 2 d , 4 d and 6 d , the baseline value was significantly shorter (P < 0.01), which was significantly shorter than the control group and the + 10 Gz group (P < 0.01) .
2. 2 The correct rate and reaction time of the labyrinth experiment in each group
Control rats accuracy increases as the number of measurements compared to baseline values increased first and then decreased (P <0. 01); + 10 Gz accuracy rats immediately after exposure when compared to baseline values and significantly decreased in 2 d ( P <0. 01), at each time point compared to control group had no significant difference; accuracy sliding group of rats immediately after exposure when compared to baseline values and 2 d significantly decreased (P <0. 01), more The control group was also significantly lower (P < 0.01) . When the reaction control rats compared to baseline values with increasing number of measurements is gradually shortened (P <0.01); + 10Gz when exposed rats immediately after the reaction with 2 d when compared to baseline values significantly longer (P <0. 05) , significantly longer than the control group (P <0. 01); immediately after exposure to the reaction when sliding rats, compared to baseline values were significantly increased (P <0. 05) when 2 d and 4 d, than the control group and also And the + 10 Gz group was significantly prolonged (P < 0.05, P < 0.01, Figure 1) .
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 seriously 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% and significantly [1, 3] about 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 test 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. Starts, sliding rats effects than + 10Gz group and control group was significantly prolonged from Exposures + Gz after 1D, the correct rate than + 10 Gz group and the control group was significantly decreased, until 4 d has not returned to normal, suggesting sliding + 10 Gz exposure operation after rats significantly reduced the ability of persistent memory 3 min, the most significant decrease in this time 2 d.
In the dark-avoidance experiment , the number of errors and the error time of the push-pull group were significantly increased at 6h and 6d after exposure compared with the control group and the +10Gz group . The incubation period was 6h , 2d , 4d and 6d after exposure compared with the control group and + The 10 Gz group was significantly shortened ; while the number of errors and error time in the +10 Gz group was significantly increased compared with the control group at 6 h after exposure , and there was no significant difference in latency between the control group and 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 adjusting the total peripheral resistance decreased reflecting increased stroke volume, etc. [8, 9]. Analysis of the reasons, probably in - when 1Gz, 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 did not resolve immediately , so at the subsequent + 10 Gz effect , the head level blood pressure was more severe than the decrease without the pre --1 Gz effect. 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 .
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