| BackgroundDeafness is the different levels of hearing loss caused by the lesions of conductive part or (and) sensory part in hearing system,and hearing nerve and each hearing system centre in the auditory pathway,and is one of the three major symptoms in otology diseases.According to the estimation of the world health organization in1996,there are near600million people with hearing lossing.According to the second national sampling survey for the disabled in2006,the number of hearing disabled and hearing speech disabled were respectively20.04million and1.27million,which accounted for27%of the total number of all kinds of people with disabilities.It seriously affected people’s daily life and work.Therefore, the prevention and treatment of deafness is still the sacred mission to the otology doctor and otology workers. With the rapid development of molecular biology, audiology, electrophysiology and ear microsurgery technology, most of the conductive deafness had been improved there hearing through surgery.However, the treatment of sensorineural deafness,is still one of the biggest problems in otology at present.The loss of cochlear hair cells in the peripheral auditory system is the most common cause of sensorineural deafness (sensorineural deafness,SNHL).The principal cause of cochlear hair cells loss is caused by the mechanical damage to the auditory receptors, or the changes of inner ear caused by noise exposure,the damages to the auditory receptors caused by ototoxic drugs such as aminoglycoside antibiotics,degenerative changes during the period of aging,etc. The changes of the auditory system have a certain degree of similarity after these pathological changes.In short,the plasticity changes of auditory center caused by hearing loss of all reasons are similar. Because of the existence of this plasticity, auditory deprivation patients may restore their auditory function. Now with the growing aging population and noise pollution in the world, deafness patients are also gradually increasing, and it is an urgent need to find a new idea of treatment of deafness.The auditory plasticity justly offers hope for otology doctor and deafness patients.To further understanding the plasticity of the central auditory system has more realistic significance.Studies have found that early auditory deprivation led to adaptive change in morphology and function of the auditory system. Through studying these changes, it may help us to further know the auditory function. In this experiment, the auditory deprived of mice model was established, and immunohistochemical was applied to observe the changes of acoustic signal reshape related protein in brain stem auditory center after auditory deprivation, in order to achieve further understanding of hearing center changes after acquired deafness.Purpose1. Through the establishment of animal model of acquired deafness by cochlea damaged,it provided a stable and reliable way to the study of the plasticity of the auditory center after hearing loss.2.To study the changes of growth-associated protein gap-43in cochlear nucleus and the inferior colliculus (inferior colliculus, IC) in mice after unilateral cochlear damage in different time points after surgery, and explore the remodeling and repair process of synapse in brain stem auditory center of mice after auditory deprivation.Materials and methods1.To establish animal model of acquired deafness.Prepare unilateral cochlear animal model in mice refering to Tian Yongsheng[1] about establishing "auditory deprived animal model in mice".To choose30Kunming mice(provided by experimental animal center of Henan province) with2-3months of age, weight25-35g, health, free of external auditory canal and middle ear infection, responsive auricle.All the experimental animals were used without using of ototoxic drugs and strong history of noise exposure. According to the principle of random, animals were divided into6groups:control group and after cochlear damage3,7,15,30,60days group respectively,each group of5only. Under surgical magnifier prism group in large type, remove the tympanic cavity with microsurgery instrument to figured out the cochlear position, and damage the cochlea.2. HE staining to observe the changes of nucleus cochlear and hypothalamic neurons form in the unilateral cochlear damage group and the normal control group.3. Using immunohistochemical technique SP method to detect the expression of GAP-43in cochlear nucleus and inferior colliculus in the control group and different time points after cochlea damaged,and using computer image analysis system to make quantitative analysis.Using SPSS17.0software for statistical analysis, the difference between each group used analysis of variance, the comparison between the two groups with independent samples t-test or calibration pairwise t-test,comparisons between groups with LSD-t test. Inspection level of a=0.05, P value of less than0.05was considered significant.Results1. Stable auditory deprivation mice model was established.2.Part of neurons of operation side cochlear nucleus and bilateral inferior colliculus after cochlear damaged appear volume contraction, protuberant disappear, pale cytoplasm staining, nuclear pyknosis and cataclastic or disappear.3.After the unilateral cochlear ear damaged3,7,15days, GAP-43of operation side cochlear nucleus were expressed on the up trend, and the the expression level significantly increased compared with normal control group and non-operated side.The difference was statistically significant(P<0.05).After30days postoperatively, GAP-43expression level decreased,but the expression level was still higher than normal control group, and the difference was statistically significant (P<0.05). After60days postoperatively, GAP-43expression level was slightly higher than that of normal control group,compared with the normal control group in the level of GAP-43expression,there was no statistically significant difference (P>0.05). The level of GAP-43were expressed no obvious change after surgery in the contralateral cochlear nucleus,and compared with normal control group, there was no statistically significant difference(P>0.05).4. After3days postoperatively, GAP-43expression levels of operated side and and non-operated side of the inferior colliculus were higher than normal control group, and the difference was statistically significant (P>0.05), and the difference between the operation side and the non-operated side was statistically significant(P>0.05); After7,15days postoperatively, expression levels were rising; After30,60days postoperatively, expression gradually decreases,but the operation side and the non-operated side was still higher than normal control group(P<0.05),except normal control group and60days postoperatively,the difference between the operation side and the non-operated side was statistically significant (P<0.05).Conclusions1. Removing the cochlea can establish stable auditory deprived animal model.2.After damaging the incoming hurt of unilateral cochlear,GAP-43were expressed an obvious dynamic change process in cochlear nuclei and nucleus colliculi inferioris.It may reflect the axonal regeneration and synaptic plasticity after hearing loss in brainstem auditory neurons. |
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