Fig. 5.
5-HT-induced inward current and increase in spontaneous burst frequency negatively correlates with intrinsic bursting frequency. A1, B1, and C1: cell-attached recording of 3 different ET cells exhibiting low (A1), intermediate (B1), and high (C1) spontaneous bursting frequency. A2, B2, and C2: voltage-clamp recording showing 5-HT-induced inward currents in the low- (A2), intermediate- (B2), and high- (C2) frequency bursting cells shown in A1, B1, and C1. A3, B3, and C3: scatterplot of the percentage difference from mean of the instantaneous burst frequency of each burst before, during, and after 5-HT in the same cells shown in A1, B1, and C1. D: scatterplot showing the correlation between 5-HT-induced inward current and cell intrinsic burst frequency. This distribution best fits to a single exponential (r2 = 0.93). “A,” “B,” and “C” represent data from cells shown in A1, B1, and C1, respectively. E: scatterplot of the relationship between 5-HT-induced current and change in bursting frequency. The black line is a least-squares linear best fit (r2 = 0.93) F: scatterplot of the relationship between 5-HT-induced increase in spontaneous (Spont.) burst frequency and the ET cell intrinsic burst frequency. This distribution best fits to a single exponential (r2 = 0.95). G: distribution of spontaneous bursting frequency recorded from a population of 288 ET cells (solid line) and predicted distribution of bursting frequencies from the same population of ET cells in the presence of 5-HT (dashed line) extrapolated with the exponential equation (y = 190.8569e−0.3542x) from F.