CISPLATIN-INDUCED OTOTOXICITY - ELECTROPHYSIOLOGICAL EVIDENCE OF SPONTANEOUS-RECOVERY IN THE ALBINO GUINEA-PIG

For 8 days albino guinea pigs (n = 48) were treated with cisplatin (ci s-diamminedichloroplatinum(II), 1.5 mg/kg body weight/day). Compound a ction potentials (CAP), cochlear microphonics (CM) and summating poten tials (SP) were recorded from the apical surface of the cochlea in res ponse to tone bursts ranging in frequency from 0.5 to 16 kHz. The reco rdings were collected in different groups of animals, 1 day, 1 week, 2 , 4, 8 and 16 weeks after cisplatin treatment, respectively. One day a fter the 8-day treatment we found frequency-dependent loss in the ampl itudes of the three cochlear potentials, with the larger losses occurr ing at the higher frequencies. In terms of threshold shift the losses were larger for the CAP than for the hair cell-related potentials SP a nd CM. A salient improvement in both CAP and CM amplitude occurred ove r the next 8 weeks. Also, the SP showed improvement. These results ind icate that guinea pig cochlear transduction recovers spontaneously aft er cisplatin injury. Recovery of the hair cell-related potentials sugg ests that recovery occurs already at the hair cell level. The question whether this recovery originates with the formation of new hair cells or with repair of damaged hair cells should be answered on the basis of subsequent morphological investigations.