The Effects Of +Gz And Noise Combined Stress On Learning And Memory In Rats

Due to it's speciality, modern war has negative impact on mental and psychological stability of military personnel of both sides. There are a number of types of stressors taking different forms such as horror, pain, anoxia, hyperthermia, coldness, acceleration, noise and so on. In field of military medicine, harmful effects caused by stress on army men are becoming more and more important and drawing greater attention from military medical specialists than ever before. Because of their special working environment, pilots have been inevitably exposed to various stressors among which positive acceleration (+Gz), noise, vibration and high temperature are always present and remain important factors threatening flying safety. Modern high-performance aircraft has good maneuverability. The positive acceleration produced by aircraft can reach +9Gz, last for 15s to 45s, and always repeatedly occur. This may exceed physiological tolerance of human beings. Learning and memory are extremely important brain functions for animal and human being, and they can reflect the normal function of central nervous system. According to previous study, exposure to sustained acceleration may cause impairment of learning and memory, exposure to noise can give rise to the deterioration of learning andmemory. However, effects of +Gz and noise combined stress on pilots have not been reported yet. So, it's of great practical significance to explore the effects of combined stress on pilot's working capacity, and this may be very useful to improve flying safety. This study has observed changes of learning and memory in rats after different +Gz and noise combined stresses exposure. The purpose of the present study was to find out the characteristics of changes of learning and memory after +Gz and noise combined stress exposure, and to further verify whether lower G training can provide protection against learning and memory impairment after this combined stress exposure.Male Sprague-Dawley rats (offered by animal experimental center of the Fourth Military Medical University) were exposed to +Gz on animal centrifuge and to noise produced by white noise generator. Changes of learning and memory in rats were observed at the time of immediately, 2d, 4d and 6d after different +Gz and noise combined stress exposure by use of Y-maze test, step-through test, and open field test.The main findings are as follows:1. High +Gz and noise combined stress may cause sustained impairment of learning and memory in rats. We investigated the effects of 4-10Gz/3min and 90dB/30min combined stress on learning and memory in rats. The results showed that, as compared with control group and noise group, the percentage of right reactions decreased significantly (P < 0.01) and the reaction time increased significantly (p < 0.01) in +Gz and noise combined stress group at all time after stress; time stay in center grille increased significantly immediately after stress exposure(P < 0.01). When compared with control group , total time and number of error increased significantly (p < 0.01) while latenttime decreased significantly immediately and 6 days after stress exposure(P < 0.01). As compared with +10Gz group, number of correct reaction in combined stress group decreased significantly (P < 0.05) and reaction time increased significantly (P < 0.01) immediately after stress exposure. It suggested that +Gz and noise combined stress may impair learning and memory of rats, and +Gz seems to contribute more to the combined effects.2. Repeated short-term high +Gz combined noise stress may lead to sustained impairment of learning and memory in rats. We investigated the effects of repeated 5 times +10Gz /45 s and noise (90dB(A)/30min) combined stress on learning and memory in rats. The results showed that, as compared with control group, percentage of right reactions decreased significantly (P < 0.01) and reaction time increased significantly (P < 0.01) in combined stress group at all time after stress exposure; total time and number of errors increased significantly (P < 0...