Potassium ion conductance of the cochlear partition: differences between the chinchilla and guinea pig

The time courses of the endocochlear potential (EP) and the K+ concentrations in the inner ear fluid under permanent anoxia were observed in the chinchilla and guinea pig using K+-selective microelectrodes. The EP following 30 min of anoxia in the chinchilla (-10.9 +/- 2.2 mV) showed a significantly less negative value than that of the guinea pig (-25.7 +/- 2.6 mV). The K+ concentration in endolymph induced by anoxia decreased less in the chinchilla than in the guinea pig. The average K+ conductance of the cochlear partition 10-30 min after anoxia in the guinea pig (0.1703 +/- 0.0792 S) was approximately 7.9 times that of the chinchilla (0.0216 +/- 0.0042 S), which is thought to be responsible for the difference of the anoxic EP between the two species.