Abstract
We observed that DPOAEs ware hardly detectable in Mongolian gerbils anesthetized with pentobarbital. On the other hand, when ketamine was used as an anesthetic, DPOAE level were generally high. The different effects of these anesthetic agents on DPOAEs became unclear when the tympanic bulla was opened. This strongly suggested that the effects might be modified by middle ear pressure. To elucidate mechanisms of the effects of these anesthetics on DPOAEs, the experiment was designed as follows; 1) investigation of ketamine effects on DPOAE in comparison with pentobarbital effects, 2) observation of the effects of middle ear pressure application on DPOAEs, 3) examinations on the influence of muscle relaxant on DPOAEs. Comparing the pentobarbital effects and effects of pressure application to the middle ear on frequency characteristics of DPOAEs, we concluded that 1) the pentobarbital administration caused negative middle ear pressure in Mongolian gerbils; 2) the generated pressure strongly suppresses DPOAEs conduction through the middle ear, thus; 3) proper selection of anesthetic agents is very important in gerbil experiments including OAE measurements.
