Time course of anoxia-induced K+ concentration changes in the cochlea measured with K+ specific microelectrodes

The endocochlear potential (EP), potassium concentration in the endolymph (Ke+) and in the perilymph (Kp+) were measured in guinea-pigs during anoxia of different duration. Specific K+ double-barrel microelectrodes with liquid ion exchanger were used. The resting K+ concentration in the endolymph was 146.8 +/- 9.2 mM and in the perilymph 3.2 +/- 0.5 mM. The following time course of events was observed in the cochlea during anoxia: 40-50 s after the arrest of ventilation the K+ concentration decreased by 0.1-0.2 mM in the scala vestibuli, which was time related to a rapid fall of EP to negative values. Perilymphatic K+ started to increase in both scalae with a latency of 2-2.5 min, reaching a concentration of about 14 mM 60 min after the arrest of ventilation. The endolymphatic K+ began to decrease after a latency of 2.5-3 min, and 60 min after the arrest of ventilation an 80% concentration (average 112 mM K+) was reached as compared to the initial value. From the comparison of K+ concentration changes with the experimental values of the negative EP, it may be assumed that the negative EP is mainly generated by the K+ gradient between the perilymph and endolymph.