Fig. 7.

Serotonin depletion affects the maturation of repetitive firing properties. A, Discharge patterns observed in motoneurons after current injection at twice the rheobase: a single action potential or a doublet (top trace), a transient spike train (middle trace), or a sustained discharge throughout the pulse duration (bottom trace). Figure adapted from Vinay et al. (2000a). B, Proportion of G–Sol motoneurons generating the different patterns shown in A. Thenumber of recorded neurons in each population is indicated at the top of each bar. The data for P0–2 were obtained from noninjected specimens (Vinay et al., 2000a). C, Mean number of action potentials (top graph) during 500-msec-long repetitive discharge in G–Sol motoneurons of sham- and PCPA-injected specimens, plotted against the magnitude of depolarizing current (normalized to rheobase). There is no statistical difference between the regression lines.