Lack of effect of cochlear round window (RW)-administered U-50488H (100 mmol) on the CM amplitudes, recorded at the three indicated stimulus intensities in the U-50488H-treated (n = 5) and control animals (n = 7), of experiment 2. At each of the three baseline (time 30, 60 and 90 min) and three post-baseline recording periods (time 120, 150 and 180 min) each point represents a mean percent change in the microphonic amplitude relative to the grand baseline mean (±S.E.M.). Open arrow at time 60 min indicates the 1μl administration of APS(50%) / DMSO(50%), delivered to the cochlear round window membrane in all animals, prior to the final 30 min baseline recording period. Filled arrow at time 90 min indicates the 2μl post-baseline round window administration of U-50488H (100 mmol) dissolved in APS(50%) / DMSO(50%) (n = 5), or the APS(50%) / DMSO(50%) solution delivered alone (n = 7).