Sequential action potentials vary in their amplitudes.

Intracellular recording of spikes was done from mice in vivo (A). B) Sequential spikes evoked by current pulses decrease in amplitudes when the intensity of input currents are raised from 0.25 nA (blue traces) to 0.55 nA (red traces). C) Spontaneous sequential spikes decrease progressively in amplitudes. D) shows the comparison of sequential spikes evoked by current pulses 0.25 nA (blue bars) and 0.55 nA (red bars). E) shows the distribution in the amplitudes of spontaneous spikes in (A).