Experimental study for modeling of noise induced hearing loss in guinea pigs

• Grant number: 06/02133-4
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2007
• End date: August 31, 2008
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Clemente Isnard Ribeiro de Almeida
• Grantee: Clemente Isnard Ribeiro de Almeida
• Host Institution: Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP). Fundação Arnaldo Vieira de Carvalho. São Paulo , SP, Brazil

Abstract

The noise induced hearing loss is a deficit that begins in frequencies around 3000Hz and develops slowly as a result of the chronic exhibition to sounds of high intensity. It is believed that about 1/5 of the population is exposed daily in their work places at sound levels potentially harmful to the audition. For best to understand an affection of such prevalence and costs for the society, it is fundamental to establish trustworthy experimental models in animals. One of the better studied animals as for its hearing anatomophisiology and comparability with the human being is the guinea pig. The models conceived for the noise induced hearing loss (NIHL) have been drawn in several animals, besides the guinea pigs, however, they are not uniform, throwing hand of the most different sound intensity, frequency and time of exposition. It wasn’t possible to find in the literature any model that was considered a pattern for use in research of NIHL, also not having studies to evaluate as much the functional result as the morphologic of the created model. Objective: To establish an experimental model, controlled functional and morphologically, that it is reliable and consistent for NIHL in guinea pigs. Material and Method: The study will evaluate the functional and morphologic repercussions of the several noise variables - frequency, intensity and duration - on the cochlea of guinea pigs. Guinea pigs will be studied, male, about 4 months of age, weighing around 400g. The animals will be accompanied in biotery. Will be studied 120 guinea pigs, 30 for each group of sound frequency. Four follow-upp periods will be created, in agreement with the central frequency of the resonant band that it will be used in the exhibition to the noise. The Bands will have as center of frequency 0,5KHz, 2KHz and 4KHz, besides one with white noise. Each continuation group will have three subgroups in agreement with the time of exhibition to the noise. The times of exhibition varied of 1 hour, 4 hours and 24hs. The animals will be put in boxes in acoustically treaty enviroment. The exposition will be controlled by decibelimeter and it will be maintained at 110dB(A) NPS. The animals will be exposed to band noises releases centered in frequencies of 500 Hz, 2000Hz, 4000Hz and white noise with Gaussian distribution in its composition. The animals will be submitted to exam of Brain stem Evoked auditory test and otoacoustic emission test before having been exposed to the noise and 1minute, 1 hour and 1 day after the exposition. After the last exam the animals will be submitted to euthanasia under general anesthesia and their cochleae will be send to exam of electronic microscopy. (AU)