Effects of combined gentamicin and furosemide treatment on cochlear ribbon synapses

•Effects of ototoxicity can be assessed electrophysiologically and morphologically.•A dose effect of gentamicin and furosemide resulted in a synaptic reorganization.•There was considerable inter-animal variability upon rising dose.•At lower doses, treatment triggered synaptic plasticity without hair cell loss.•At higher doses producing hair cell loss, there was a reduction of synapses.