Isolation entry components by applying TMPA solution separately to the apical and basal regions of the cochlea. A silicone “dam” (shown black in the inset schematic) was built to prevent fluid from spreading throughout the entire bulla. In experiments where applied fluid bathed the basal turns only (Panel A, n=2), initial sample concentrations (samples 1 and 2) were low, consistent with low TMPA levels in the apical turns. In experiments where applied fluid bathed the apical turns only (Panel B, n=2), initial sample concentrations were high, consistent with high TMPA levels in the apical turns. Concentrations were normalized as a percentage of the applied concentration. Bars indicate standard deviation.