Chronic effects of loop diuretics on the guinea-pig cochlea.

Groups of pigmented guinea pigs (weighing 480 to 650 g at the start of the experiment) were given daily intraperitoneal injections of 16 mg/kg bumetanide or 10, 20 or 40 mg/kg furosemide over a period of 4 weeks. Two weeks following the last diuretic dose the animals were anaesthetized with urethane and the responses of single auditory nerve fibres to pure-tone and click stimuli were recorded. The tuning of individual units, as measured by Q10 dB values of frequency threshold curves, tended to be more affected than threshold at characteristic frequency by both loop diuretics. Light microscope examination of treated cochleas suggested greater effect of the drugs on the organ of Corti than on stria vascularis.