(A) Sample traces show slowly adapting type 1 (SA1) impulses elicited by a 20-µm whisker hair deflection in normal bath solution (control, upper panel) and in the presence of 10 μM serotonin. (B) Summary data of the SA1 frequency at different time points during whisker hair deflection under the following conditions, in normal bath solution before serotonin application (control, circles, n = 6) and following the bath application of 10 μM serotonin (squares, n = 6). (C) Summary data show that bath application of 10 μM serotonin (squares, n = 6) significantly increases SA1 impulses when compared with control (circles, n = 6) at each displacement step. Displacement steps were from 5 to 35 μm at an increment of 5 μm. (D) Sample traces show SA1 impulses elicited by a 20-µm whisker hair deflection in normal bath solution (control, upper panel) and in the presence of 2 mM serotonin (lower panel). (E) Summary data of the SA1 frequency at different time points during whisker hair deflection under the following conditions, in normal bath solution before serotonin application (control, circles, n = 6) and following the bath application of 10 μM serotonin (squares, n = 6). (F) Summary data show that bath application of 2 mM serotonin (squares, n = 6) significantly decreases SA1 impulses when compared with control (circles, n = 6) at each displacement step. Data represent the mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; two-way ANOVA with Bonferroni post-hoc tests.