| Objective: (1) To study the change of hearing threshold value and latency of Ⅰ , Ⅲ, Ⅴ wave and Ⅰ - Ⅴ, Ⅲ- Ⅴ wave tested by Auditory Brainstem reflect(ABR) that effected by Sodium salicylate. Discover the impact of rat hearing in different periods after intraperitoneal injection sodium salicylate. (2) Determine the position of calpain 1 in the inferior colliculus. To investigate the expression of calpain 1 in the inferior colliculus of SD rat effected by sodium salicylate on.(3) Explore the relationship between the calpain 1 and hearing impairment caused by sodium salicylate.Method: (1) The system of the United States Bio-logic multifunction electrophysiology instrument used to detect the ABR texting. The SD rats that results of hearing threshold test were less than 40dB SPL classified as experimental subjects. (2) Choosed 72 rats that hearing threshold test were up to standard, male or female, and weighing between 200g and 250g, divided into four groups ,randomly. Each group of 18 rats. Control group: intraperitoneal injection of saline; sodium salicylate group(ss Group): intraperitoneal injection of sodium salicylate; calpain inhibitor group (ALLN Group): intraperitoneal injection of calpain inhibitor ALLN (N-acetyl-Leu-Leu -Norleucinal); ss +ALLN group: intraperitoneal injection of sodium salicylate and ALLN. The does of each rat calculated according to body weight, sodium salicylate dose of 350mg / kg · d, calpain inhibitor dose of 10mg / kg · d, and the dose of saline group as the same volume as ss group. (3) Before treated , each group of rats feeding in specific pathogen free (SPF) animal room for adaptation. In the periods of one day before saline and drug injection and 1 week after injection, 4 weeks after injection, text the hearing threshold detection auditory brainstem reflect of each rat, Ⅰ, Ⅲ,Ⅴ wave latency and Ⅰ - Ⅴ wave, Ⅲ- Ⅴ wave wave latency, and selected 6 rats from each group randomly after measurement,fixation with 4% paraformaldehyde perfusion through the heart and then taken out inferior colliculus, fixed by paraffin and detected expression of calpain 1 by immunohistochemistry.Result: (1) After intraperitoneal injection of Sodium salicylate, the more time intraperitoneal injection of Sodium salicylate, the hearing thresholds of ss group were worse (P<0.01), the incubation period of Ⅰ ,Ⅲ,Ⅴ and Ⅰ -Ⅴ,Ⅲ-Ⅴwave were extended(P<0.05), (2) The expression of calpain 1 in the nerve cell of inferior colliculus were increased (P<0.01).Conclusion: (1) Long-term use of ss can cause hearing loss in rats, and with prolonged use, the greater the value of the hearing threshold of the rats. (2)Normal hypothalamic neurons expressed a small amount of the calpain 1,Long-term use of ss can cause calpain 1 expression increased in central nucleus of inferior colliculus, and with prolonged use of ss, The more amount of calpain 1. (3) Calpain participated in the damage process, and the degree of hearing impairment was proportional to calpain 1 expression. Application of calpain inhibitors can be reduced to the damage of calpain. |
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