大鼠听觉发育中听觉敏感度及时间分辨率的变化

摘要

Objective To evaluate the correlation of the development of auditory acuity and temporal processing using prepulse inhibition of acoustic startle response. Methods A reflex modification paradigm- gap- PPI was used to evaluate the shifts in gap detection thresholds in rats throughout development, beginning on postnatal(P)day P14, P16, P18, P22, P26, P30 and P35； under 8～32 kHz and 1 ～48 kHz background noise respectively.Meanwhile we investigated the hearing frequency development by ABR test on exactly the same test day. Results ABR showed that the thresholds 1, 2 and 4 kHz matured at around P26 and P22 for 16 and 32 kHz and P18 for 8 and 48 kHz. As a result, until P26 did the auditory acutiy matured at every frequency. In the gap-PPI test, the gap detection thresholds lied around 50ms for P14, 25ms for P16, P18, P22, P26, and 10 ms for P30 and 8 ms for P35 under 8～32 kHz background noise. While under the background noise of 1～48 kHz, the gap thresholds decreased significantly(p=0. 013), lied around 25 ms for P14, 15ms for P16 and P18, 10ms for P22,P26, P30 and P35. But the temporal processing matured at around P30 both in two background noise. Conclusion During the development of auditory system, the development of temporal processing falls behind that of auditory acuty.%目的 运用听觉惊跳反射前抑制方法观察大鼠听觉系统发育过程中听觉敏感度和时间分辨率的改变及两者之间的时间相关件.方法 选用日龄为14、16、18、22、26、30、35天的新生SD大鼠各20只,各日龄大鼠分为2组,每组10只,每个日龄组的大鼠均进行听性脑干反应(ABR)测试和听觉惊跳反射前抑制测试,一组大鼠在测试时标记的背景噪声频率为1～48 kHz,另一组大鼠的背景噪声频率为8～32 kHz.结果 1、2和4 kHz ABR阈值在第26天、16和32 kHz ABR阈值在第22天、8和48 kHz ABR阈值在第18天与第35天比较差异无统计学意义(P>0.05).因此,生后第26天,大鼠听觉系统各频率已发育完全,听敏度已达到正常成年大鼠的水平.听觉惊跳反射前抑制测试表明当背景噪声为8～32 kHz时,第14天大鼠的间隔阈值为50 ms左右;第16、18、22、26天大鼠的间隔阈值为25 ms;第30天大鼠的间隔阈值为15 ms;第35天大鼠的间隔阈值为8 ms.当背景噪声为1～48 kHz时,间隔阈值明显下降(P=0.013),第14天大鼠的间隔阈值为25 ms;第16、18天大鼠的间隔阈值为15ms;第22、26、30、35天大鼠的间隔阈值为10 ms.但在两种背景噪声下,时间分辨率均在第30天发育成熟.结论 在大鼠听觉系统发育过程中,时间分辨率的发育落后于听敏度的发育.