In order to detect NITTS and NIPTS in guinea pigs, the influence on the latency of AP (N
1) after white noise exposure was studied electrocochleographically. In this series, the guinea pigs were 250 grams to 500 grams of body weights with normal Preyer's reflex.
Electrocochleographic recordings were repeated several times before and after white noise was exposed to the animals under general anesthesia with pentobarbital sodium (45mg/kg i. m.). The stimulation sound used in this study was click, and was given through a ear tube. A positive needle electrode was placed in the external ear canal, and a negative needle electrode in the ipsilateral ear lobe, and the ground in the ipsilateral leg. The responses were averaged 200 times and recorded on a X-Y recorder. The experimental conditions of white noise exposure were as follows:
The results wére as follows:
1. Under the experimental conditions of A, B, C, D and F, the latency of AP was prolonged immediately after white noise exposure. However, one day after or one week after white noise exposure the latency of AP returned completely to the pre-exposure level. In these experimental conditions, therefore, white noise exposure were considered to induce NITTS in the guinea pigs.
2. Contrary to the above, in the experimental conditions of E and G, the latency of AP was prolonged even one week or 2.5 months after white noise exposure. Thus, these two experimental conditions were considered to have induce NIPTS in the guinea pigs.
3. From these two results, the latency of AP in electrocochleography was considered to be one of the parameters to detect NITTS and NIPTS in the guinea pigs.
View full abstract