Increased fatigue of cochlear potentials after injection of KCl solution in the perilymph

Cochlear microphonics (CM), action potentials (AP) and endochochlear potential (EP) were recorded on guinea pigs. The introduction of a small quantity of KCl solution (0.1 N) in the perilymph provoked a moderate decrease of CM and AP. During the period of depressed but stable amplitude, the presentation of intense sounds provoked an exaggerated susceptibility to fatigue and a delayed recovery. Similar changes were observed in the evolution of EP. However, the recovery was slower for EP than for CM. The results, as a whole, suggest that the fatigue which is manifested in the depression of cochlear potentials is related to a leakage of potassium ions from endolymph to fluids spaces within the organ of Corti.