Ultrastructural and electrophysiological studies of acute ototoxic effects of furosemide

Previous studies of the effects of ethacrynic acid on the inner ear following intraperitoneal injection of the diuretic have shown a progression of reversible changes occurring in the stria vascularis. The time course of these changes approximately parallels alterations in endolymphatic potential (EP). In this report, some preliminary findings concerning the effects of furosemide after intraperitoneal injection of 80 mg/kg are described. EP declined over a longer time course than that recorded with intravenous injection. Cochlear microphonic (CM) and compound action potential (CAP) also declined but to differing degrees. In the stria vascularis a progression of changes was apparent. In general, the changes were similar to those observed following ethacrynic acid intoxication and affected marginal cells, intermediate cells and strial capillaries. The upper basal turn of the cochlea was affected first and the damage spread apically. In the organ of Corti, stereocilia on the outermost row of outer hair cells were disorganized. This was apparent in approximately the same region as initial strial effects and was only observed when strial derangement was quite marked.