A, superimposed current traces obtained in an E17 vestibular neurone showing the current growth when the interval of two paired pulses (100 ms, −42 mV) increased from 0 ms up to 4.4 s (step 100 ms). B, plot of the mean normalized current amplitudes as a function of the interpulse interval. The relationships were fitted with two exponentials (continuous line). The time constants were 102 ± 13 and 1281 ± 41 ms, and amplitudes 0.38 ± 0.03 and 0.53 ± 0.02 (n = 22) for the fast and slow components, respectively.