Figure 4.

Effects of auditory inputs on the potassium current after hatch. A, B, Auditory inputs were attenuated or elevated between P0 and P3–P5 by tympanic membrane removal, columella fixation, cochlea removal at P0, or by exposing animals to noise during the indicated period. C, Potassium current in high-CF (left, blue) and low-CF (right, red) neurons at P3–P5. Top, Cochlea removal. Upper middle, Columella fixation. Lower middle, Tympanic membrane removal. Bottom, Noise exposure. D, Voltage dependence of activation curves. The curves were fitted by a double Boltzmann equation, showing low-voltage-activating (Kv1, black) and high-voltage-activating (Kv3, gray) components (see Materials and Methods). Percentage of the Kv1 component is specified at right in each panel. Vertical and horizontal arrows indicate −42 mV (C, D). E–G, Maximum amplitudes. Kv1 current (E), Kv3 current (F), and total current (G). Control is a replot of Figure 2 (P3–P5). V_1/2 and slope factor of Kv1 and Kv3 currents did not change after the manipulations (p > 0.05, ANOVA). ^#p < 0.05 between tonotopic regions. *p < 0.05 and **p < 0.01 compared with control.