The peaks of active traveling waves also shifted basally as the stimulus level increased (Figures S1D and S1E). The high gain and nonlinearity were completely abolished when the active process was interrupted by anoxia (Figure 1E), which additionally displaced the wave’s peak toward the cochlear base. The phase profiles of traveling waves displayed slopes that were dependent on stimulus level in healthy cochleas

but not following anoxia (Figure S1F). These phenomena reflect the loss after anoxia of a tuned, Selleck Talazoparib tonotopically distributed amplification mechanism that enhances a traveling wave as it approaches the characteristic place at which it peaks. To investigate the interplay between active cellular forces and the spatial shaping of an active traveling wave, we developed an optical technique that locally and significantly perturbs electromotility. Small carboxylic acids inhibit prestin-based motility; salicylate Rucaparib in vitro is the most effective of these blockers (Tunstall et al., 1995; Oliver et al., 2001). Our technique uses 4-azidosalicylate, the azide group of which forms covalent bonds upon activation by ultraviolet (UV) light

(Figures 2A and 2B). The compound is therefore an inhibitor that forms an irreversible complex with prestin, effectively disabling it. We initially characterized the effect of 4-azidosalicylate on somatic motility in HEK293T cells transfected with prestin-eGFP. Motility was deduced from measurements of a cell’s voltage-dependent capacitance, which reflects the gating currents that accompany conformational changes in large ensembles unless of prestin molecules. Capacitance was measured from phase changes in the currents elicited by sinusoidal membrane-potential perturbations at different holding potentials (Fidler and Fernandez, 1989). When

washed onto prestin-transfected HEK293T cells, 4-azidosalicylate largely abolished somatic motility as inferred from the linearization of the voltage-capacitance relation, an effect that was reversible upon washout (Figure 2C). UV irradiation had no effect on motility in control medium (Figure 2D). If a cell incubated in 4-azidosalicylate was exposed to UV light, however, motility did not return after washout (Figures 2E and 2F). The cell nonetheless remained healthy as assessed by visual appearance and by the absence of leakage currents. Because the nonlinear capacitance measured in prestin-expressing cells cannot be dissociated from mechanical motility (Santos-Sacchi, 1991), photoinactivation presumably elicits a concurrent attenuation of the latter. We nonetheless confirmed that photoinactivation affects the somatic motility of isolated outer hair cells.