Changes of summating potentials and morphology in theguinea pig cochlea during anoxia

I.IntroductionThesummatingpotcntia1s(SPs)rcprcscntsaspccificbioe1cctronphenomenonofthecoch1ea.C1inica1lythedominant-SPisnowtakenasasignofrecruitmcnt.However,themechanismofrecruitn1cnt,exccptinMcnicrcdiscase,isnotentireIyunderstood.Thedynamicchangcsinamp1itudcandpolarityofSP,lnrclationtothethrcsho1dshiftofcompoundactionpotential(CAP),SPandcndocochlcapotcntial(EP)inthescalcmcdiawcrcexaminedatonehmewithsing1cmicropipctduringandaftcranoxia.Also,themorpho1ogicchangesinthein-nerhaircc11s(IHC…

Changes of summating potentials and morphology in the guinea pig cochlea during anoxia

The dynamic changes in CAP, and EP in the scale media were examined with single micropipet during anoxia and reventilation with oxygen. Also, the morphologic changes in IHC, OHC and synapse were observed in this experiment. It was found that the amplitude of SP and EP values declined with alteration in polarity of these value. The changes in polarity and amplitude of SP followed the changes of CAP threshold induced by anoxia. The histologic examinations revcaled no cvidence of acetylcholinesterase (AChE) alteration in the synapse and no succinict 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 change of SP polarity from positive tonegative during anoxia is due to the loss of mudulation 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.