[ comparison of effects of toluene, especially noise and toluene along with noise per auditory brain stem response on rabbit]

An increase more than definite limit in sound pressure level is harmful for health mean while, organic solvents like toluene are used in industrial processes with noise widely. So, this study was going to investigate the relationship between toluene [1000ppm], noise and toluene along with noise [frequencies 4000 and 8000 Hz] per auditory Brain Stem response [ABR] on rabbits being exposed to these contaminants. This survey was done in experimental method on 48 three months old, male adult white New Zealand rabbits [1800 +/- 200 g body weight], in nine groups which were exposed to toluene [1000 ppm], noise [4000 Hz], 100 dB SPL, combination of toluene and noise conducted using click and tone burst stimuli in 110dB sound pressure level. Then the results of ABR test of groups exposed were analyzed by SPSS software. One-way variance [ANOVA] analysis was used to compare the groups and Turkey test was applied as a post hoc test for comparison among the groups. P values were obtained by Turkey test. t-test was conducted for comparison of ABR test results after and before exposing groups. Differences at the level of P<0.05 were considered statistically significant. The results of the study showed that Exposing rabbit's to combination of toluene and noise caused hearing impairment in all of frequencies auditory especially in frequencies 250, 500 and 1000Hz. So that, wave five in ABR test [tone burst stimuli] didn't formed in 250-1000 Hz 4.84 +/- 0.07 ms, group exposed to toluene 5.18 +/- 0.07ms, noise group [4000hz] 5.5 +/- 0.07 ms and in combination noise and toluene group [4000Hz] 5.79 +/- 0.07 ms. The mean of latency time of V wave in control was compared to that group noise group P=0.01, toluene group P=0.07 and combination noise and toluene group P=0.0001. According to the result of this study, both toluene and noise exposure caused the rabbits in hearing impairment but combination of toluene and noise exposure in frequencies of 4000Hz and 8000Hz was much worse than hearing impairment. So that, the ABR test on rabbits didn't formed V wave in low frequency

Effect of sound conditioning on protection of hearing and plasma antioxidant activity in rabbits

Noise is one of the major physical pollutants in present societies. Sound conditioning is used as means of protecting against noise-induced hearing loss. The status of plasma antioxidant system during sound conditioning is important. To study possible involvement of plasma total antioxidant ability in noise-induced hearing loss and sound conditioning. This study was carried out on 24 male white New Zealand rabbits [6 in each group]. The rabbits were assigned to the following four groups: [1] Noise exposure [250Hz-20000Hz, 110 dB for 8h/day for 12 days], [2] Conditioning noise exposure [80dB for 10 days and 110 dB for 12 days], [3] Noise exposure [80 dB] and [4] control group. Auditory Brain stem Response [ABR] was measured and compared in all pre- and post-exposures groups. Plasma antioxidant power was also measured post exposure. FRAP was assayed in plasma sample collected from each animal using TPTZ reagent. The ABR assay using click in different experimental groups showed that the absolute latency of 5[th] wave generation was statistically significant in first group as compared to other groups [p=0.0001]. Likewise ABR assay using tone burst showed a higher absolute latency observed in group 1. FRAP assay indicated that the antioxidant parameters were suppressed in group 1 when compared with data obtained from other groups [p<0.05]. The ABR results found in our study, confirmed sound conditioning in rabbits exposed to 80 and 110 dB. Furthermore, changes in FRAP in rabbits studied in our experiment was indicative of involvement of antioxidant system in sound conditioning however, further studies needed