Origin of the endolymphatic DC potential in the cochlea and ampulla of the guinea pig.

In order to determine the origin of the endolymphatic DC potential, potentials in the cochlea (CEP) and ampulla of the posterior semicircular canal (AEP) were recorded simultaneously in normal control guinea pigs and guinea pigs treated with aminoglycoside antibiotics. There were no significant differences in the resting levels of the CEP and AEP between the two groups. In the normal control guinea pigs, the endolymphatic potential of each animal decreased differently during anoxia and after an injection of furosemide. In kanamycin-treated guinea pigs whose cochlear hair cells were damaged, the CEP response to 150s of anoxia was quite different from that of the control animals: it decreased more slowly and did not reach a zero level. In contrast, the AEP had a normal response to anoxia. In streptomycin-treated guinea pigs with damage to the ampullary hair cells, the situation was reversed: the AEP responded normally while the CEP responded abnormally. These findings indicate that the AEP is most likely independent of the CEP and is generated within the ampulla. They also indicate that sensory epithelial in the cochlea and ampulla play an important role in the maintenance of the CEP and AEP, respectively.