Effect Of Strong Noise Acute Exposure On The Body And Cognitive Function Of Guinea Pig

Noise is a kind of harmful factor in nature, social life, industrial production,transportation, urban construction, military training and combat, and a variety of other professional environment. A large number of people exposed to different levels of potentially harmful noisy environment. Research of biological effects shows that the damage of noise on the body is various, it will not only directly damage auditory system, but also cause different degrees of non-specific damage of no-auditory system such as neuroendocrine system, cardiovascular system, immune system, respiratory system, digestive system, reproductive system, cognitive function and so on. The damage degree are decided by the nature of the noise, intensity, frequency, exposure time, individual susceptibility and so on. At present, a lot of research from different angles had been done, but the biological effect of strong noise and its mechanism are still not well studied, and the effective preventive measures are still scarce.Therefore, this research takes adult guinea pigs as the research object. They are exposed continuously to white noise of 120 d B for 4 hours.The behavior of guinea pig are recorded by a real-time video camera; Morris water maze test are taken to evaluate its space cognitive ability; spontaneous activity test are taken to observe the changes of spontaneous activity; auditory brainstem response are used to detect the effect on auditory function; Using cochlear pave piece, immunohistochemistry and confocal laser scanning microscope, we observe the morphological changes of cochlear hair cells;Enzyme linked immunosorbent test are taken to test the change of stress hormones, biochemical metabolic enzymes, neuropeptides,etc. Using paraffin pathological section and H.E staining,we made gross and microscopic pathological specimens of temporal lobe cortex, hippocampus, hypothalamus and cerebellum and gross and microscopic pathological morphological changes of the other large organs.Through the above experiments, we want to discuss the effect of strong noise on organism and cognitive function and its characteristic, and look for some sensitive biomarkers, which are related to noise-inducing damage of body and cognitive.Thus,these results can lay foundation for the further research on damage mechanism andmilitary applications. The research content is divided into four parts, the main research results are as follows:1. Effects of Strong noise on the activity and cognitive function of guinea pigsWe use camera, Morris water maze and spontaneous activity box to compare the differences on behavior, activity and spatial learning and memory ability between the noise exposure group and the control group of guinea pigs.1.1 BehaviorWe use the real-time video to observe and analysis the effect of strong noise on the behavior of guinea pigs. The results show that in the early period of the strong noise exposure(5 minutes) : the guinea pigs appear to be terrified and behave escape response, then gradually to be quiet, back to the sound source to get rid of the noise source. hair stands, eyes slightly open, etc.The later period of the noise exposure(1-3h) : just stood, scratching their heads, listlessness, defecation, etc.After the exposure :some show anxiety in circles and exclaimed, some became dense, slow to stimuli and not active,some animals become hemiplegia or even die.The above results show that strong noise may cause neurobehavioral dysfunction.1.2 Spacial learning and memoryWe used the Morris water maze test to evaluate the ability of spacial learning and memory. The results show that after strong noise exposed, the average latency to the plate became much longer in the experiment group than the control group. Plate form entries and time spend in the target zone are both much less in the experiment group.These results indicate that strong noise may impair cognitive function, but this effect is temporary and reversible.1.3 Spontaneous activityWhat is more,we also use the spontaneous activity box to analysis the difference of activity between the two groups. The results show that compared with the control group, the total distance,moving duration and rest times are much shorter in the experiment group,while the time of rest are much longer. The average speed became slower but doesn’t significantly. Seven days later, we performed the same test and find that the difference between the two groups are much less. These results show that strong noise can impair the motor function,but this can be reversed in the later days.With these experiment performed,we are sure that strong noise can impair the neuro-cognitive function. Animals affected became abnormal activity, lower spontaneous activity,impaired spacial learning and memory etc.2. Effect of strong noise on auditory function and structure of guinea pigsNoise can produce multiple systems harm to the body, of which the most seen is hearing damage, it can produce specific damage to the auditory system directly,causing noise deafness, its main reason is the loss of outer hair cells causd by cochlear structure damage. So the assessment of outer hair cells damaged after noise exposure is important on judging the degree of noise deafness, the region and the degree of damage depends on the noise frequency, intensity and duration. So in order to clarify the effect of strong noise at 120 d B exposure for 4h on auditory function and form. we conducted the following study.2.1 The test on hearing functionAfter guinea pigs being exposed to strong noise of 120 d B for 4h, we used auditory brainstem response to detect and judge the influence on auditory function.Results showed that: compared with control group, the hearing threshold of guinea pigs had been significantly increased, the average hearing threshold shift reached up to 48 d B, it showed strong noise had caused irreversible damage on the auditory function of guinea pigs.2.2 The observation of microscopic pathological morphology on cochlearIn order to further determine the influence on the shape and structure of the hearing system by strong noise, we observed the pathological morphology of cochlear which was the most easy to be damaged by the noise,and we saw that part of the cilia of hair cells appeared lodging and extensive loss, hair cells also arise different degrees of structure damage after strong noise of 120 d B exposed for 4h. The morphological changes of hair cells is the pathological basis of noise-induced hearing loss.In conclusion, auditory brainstem response and cochlear morphology observation study suggests that: strong noise caused lack, apoptosis and structural damage of cochlear hair cells, causing the irreversible hearing loss, which showed that strong niose exposure have caused significant damage to hearing structure and function.3. Effects of strong noise on physiological and biochemical indexes in the blood3.1 Changes of blood routineThe results of blood routine test showed that: The number of Erythrocyte,Hemoglobin and Platelets in the blood increased significantly, but the level of Lymphocytes and Eosinophils reduced obviously, and the rest of the cell has a tendency to rise, but no statistical difference. These were consistent with previous research results. The above results suggested that strong noise have certain effect on the blood routine, and blood system involved in the process of noise stress. Reduced lymphocytes also suggests noise caused the immune system suppression, especially the cellular immune function.3.2 Changes of biochemical metabolic enzymes in the serumAutomatic blood biochemical analyzer test results showed that the content of ALT, AST, LDH and CK in the serum increased significantly after strong noise exposed for 4h, above all,CK levels has the most obvious change. It showed that strong noise can cause a variety of biochemical metabolism enzyme disorder in guinea pigs, causing a certain extent damage to the structure and function of the brain,heart, liver, kidney and other organs, it also suggested that CK can be considered as a sensitive indicator for the injury of body and brain caused by noise.3.3 Changes of stress hormones and c-reactive protein in the serumEnzyme-linked immunosorbent assay results showed that after white noise at 120 d B exposed for 4 h, The content of hormones in the serum including CRH,ACTH,CORT, AVP, OT, NE and CRP were reduced significantly, while the level of ALD and E were increased significantly, the above indexes had statistically significant differences compared with control group, especially CORT and NE changed the most obvious, Ang Ⅱ had a tendency to rise, but with no statistical difference.3.4 Changes of neuropeptides and neuroglobin in the serumEnzyme-linked immunosorbent assay test results showed that the level of NPP,NPY and NGB in the serum of guinea pig were significantly increased after strong noise at 120 d B exposed for 4h.It hints that these indicators may have a certain value to the quantitative evaluation of niose-inducing cognition impairment.After the acute exposure for 4h of stong noise, the content of physiological and biochemical indexes such as stress-related hormones, biochemical metabolism enzyme, neuropeptides and neuroglobin in the serum of guinea pigs had significantchange except AngⅡcompared with the control group, especially the level of CORT,CK, NE, NPY, NPP and NGB had the most significantly change than the control group which suggests they may be considered as a sensitive markers of noise-inducing body and cognitive impairment.4. Effect of strong noise on the morphological structure of viscera in guinea pigs4.1 Observations of Gross pathologyFollowing by exposure to strong noise, we immediately conduct the experiment of gross anatomy in guinea pigs and we can see that : it appears different degrees of damage in several internal organs of guinea pigs, and visible diffuse hyperemia of cerebral cortexand and lung are the most obvious.4.2 Observations of microscopic pathologyWe observed visceral paraffin pathology biopsy of guinea pigs under the optical microscope,it showed that : after strong noise exposed for 4h, the lung appeared congestion, edema and drainage, and there were some pathological changes in epididymis such as several lymphocytic invasion, angiectasis and hyperemia; and we can also see the mild fallen-off in gastric mucosa and Mild edema in the lining of the stomach.There are no obvious pathological changes in other organs such as the cortex,hippocampus, cerebellum, hypothalamus, heart, liver, spleen, kidney and pancreas.The above results suggest that strong noise can cause morphological structure changes in multiple orans and systems of guinea pigs, such as neuroendocrine system,respiratory system, digestive system and reproductive system. The pathological results directly reveal the organs suffering from the damage of strong noise from the view of morphology.In summary, this study completed the detection of damage effect in the field of neurobiology and pathophysiology to guinea pigs under the condition of strong noise acute exposure. We found that it can cause the following symptoms of guinea pigs after strong noise of 120 d B exposed for 4h. Firstly, the guinea pigs appeared obvious neurocognitie dysfunction, such as discomfort, abnormal behavior, cognitive impairment and so on. Secondly, it damaged the cochlea hair cells structure, which resulted in various degrees of damage in hearing loss. Thirdly, it led to pathological morphology and function damage of different degrees in multiple organ system such as brain, heart, lungs, liver, kidney, stomach, testicular and so on. What’s more, itpresented different trend and level changes of stress hormones, biochemical metabolic enzymes, neuropeptides,etc. which are related to noise-inducing damage to the body and cognition. These findings verified the effector organs and effector molecules of strong noise from the aspects of function and form. And it confirms that strong noise can cause different damage to the structure and function of multiple systems and neurocognitie function, its effect on health is systemic. We also preliminarily screening some sensitive indicators including CORT, CK, NE, NPY, NPP and NGB,which related to the body and cognition impairment. The changes of these indicators in the serum are useful to quantitative description to damage effect of strong noise on the body and cognitive impairment, and this research provides a reference for the further study of damage mechanism.