Effects of Hypothermia on CAP Adaptation

Abstract

The effect of inter-click interval (Δt) and stimulus intensity on compound action potential (CAP) adaptation was explored in six guinea pigs. In addition, the effect of hypothermia on CAP adaptation was investigated in the same animals. CAP was elicited from the exposed round window through a retroauricular incision using a silver ball electrode. After obtaining the baseline data, hypothermia around 34°C was obtained. Click was used to track the threshold shifts. All animals showed almost no threshold shift throughout the experiment. Click train consisted of 10 clicks in three different Δts and intensities was delivered through the loud speaker placed in front of animals ear. The bigger Δt or the higher intensity, the smaller CAP adaptation occurred in normal temperature. Hypothermia induced decrease in CAP amplitude and altered adaptation pattern to click trains. Decreased CAP amplitude was induced by desynchronization. It is concluded from our results that hypothermia affects CAP adaptation process without changing threshold. It is proposed that CAP adaptation would be useful for detection of some inner ear dysfunction.