Ototoxicity of ethacrynic acid was investigated by measuring endocochlear potentials (EP), whole nerve action potentials (AP) and cochlear microphonics (CM) in 19 guinea pigs. Ethacrynic acid induced EP depression decreased AP and CM amplitude without significant change in AP latency. In AP-input-output functions, disappearance of the so-called L-part was found in several cases after ethacrynic acid treatment. Results indicate that AP and CM in ethacrynic acid intoxication decreases mainly as a result of EP depression, although the possibility of another cochlear inhibiting mechanism still remains.
