Blocking effect of radio-contrast media on cochlear depression

Furosemide injection was used in a total of 72 guinea pigs to induce a cochlear dysfunction similar to the sensorineural loss associated with sudden deafness. Prior to the furosemide administration, 38 of the animals were treated with an injection of one of four radio-contrast media; methylglucamine and sodium diatrizoate, sodium iothalamate, methylglucamine and sodium iodamide, and methylglucamine diatrizoate. In the control animals, receiving only furosemide, both endocochlear potential (EP) and cochlear microphonic (CM) underwent a severe depression followed by recovery and subsequent secondary depression. Animals pretreated with one of the first three compounds showed little or no EP or CM depression. Animals pretreated with the fourth, methylglucamine diatrizoate, showed the same EP depression as the control animals. The possible mechanism for this blocking effect and its significance in the clinical treatment of sudden deafness is discussed.