Cochlear microphonics and SDH activity in the hair cells under anoxia.

Cochlear microphonics and succinic dehydrogenase (SDH) activity of the hair cells during anoxia were studied in guinea pigs. After injection of the glucose-glucose oxidase mixture into the cerebellomedullary cistern, the deprivation of the oxygen tension in CSF and perilymph was measured in different time courses. In CSF, oxygen tension was reduced to zero within 60 min while in perilymph the maximal reduction was about a half the original level. The cochlear microphonics responded well to the oxygen tension deprivation in the perilymph. SDH activity, particularly in the outer hair cells was quite parallel to the oxygen tension in perilymph and also to the behavior of the cochlear microphonics. The present results indicate a close relationship between the electrophysiological and histochemical findings and that cochlear microphonics represent the function of the outer hair cells only.