[The changes in the summating potential and morphology in the cochlea of guinea pigs with anoxia]

The dynamic changes in the CAP, SP and EP in the scale media were examined with single micropipet during anoxia and reventilation with oxygen. Also, the morphologic changes in the IHC, OHC and synapse were observed in this experiment. It was found that the amplitude of the SP and EP values declined with alteration in polarity of these value. The changes in polarity and amplitude of the SP followed the changes of CAP threshold induced by anoxia. The histologic examinations revealed no evidence of acetylcholinesterase (AChE) alteration in the synapse and no succinic dehydrogenase (SDH) changes in IHC appeared. However, the activity of SDH in the OHC decreased. The results suggest that the polarity and amplitude of SP were influenced passively by the changes of EP value. In addition, the changes of SP polarity from positive to negative during anoxia is due to the loss of modulation process of OHC to IHC, while the SP polarity from negative to positive during the supply of oxygen is caused by regain of the modulation process of OHC.