Figure 6.

5-HT modulates the electrical activity of PPG neurons. (A,B) Spontaneous firing rate recorded from PPG neurons in loose-patch cell-attached configuration. Periods of the original recordings at time points i, ii, iii, and iv are displayed below the graphs of instantaneous firing rate. Some PPG neurons are activated by 5-HT (A), whereas others are inhibited (B) or do not change firing rate (not shown). (C) Box and whiskers plot of data from cells that were activated (n = 5 cells) or inhibited (n = 7 cells) by 5-HT and from cells that did not change their firing rate in response to 5-HT (n = 4) (data from 8 mice). A one-way within subjects ANOVA revealed a significant effect of 5-HT in the activated (p < 0.01) and inhibited (p < 0.01) cells but not in the unresponsive cells. A post-hoc analysis (Tukey) revealed a statistically significant increase in firing rate compared to baseline in the activated cells (p < 0.01) and a decrease in the inhibited cells (p < 0.05). (D) Left panel: Simultaneous recording of firing activity in attached patch configuration (bottom trace) and of intracellular Ca²⁺ (top trace, i.u.: intensity units) revealed a positive correlation between firing rate and intracellular Ca²⁺ concentration. The black bar indicates application of 20 μM 5-HT. Right panel: Correlation between changes in firing rate and intracellular Ca²⁺ levels for four individual cells analyzed. Each cell is represented by a unique color, individual data points are represented by dots and a linear fit to the data is plotted in the same color (data from 3 mice).