A comparison of the effect of cochlear perfusion with ouabain on summating potentials and distortion product otoacoustic emissions in the guinea pig.

In order to investigate whether or not the summating potential (SP) and the 2f1-f2 distortion product otoacoustic emission (DPOAE) are due to related cochlear non-linearities, their behavior was studied in the guinea pig after intracochlear perfusion with ouabain and subsequent rinsing. The SP was evoked with either 4 or 8 kHz tone bursts, and the 2f1-f2 DPOAE was evoked with simultaneous presentations of 6.6 and 8 kHz continuous tones. After ouabain perfusion, DPOAE was dramatically reduced while the SP underwent only a small reduction. After rinsing out the ouabain with artificial perilymph, the DPOAE showed partial recovery while the SP displayed a large and long-lasting increase when compared to its a initial value. These results suggest that the non-linear processes giving rise to the SP and DPOAE are not identical.