Figure 4.
5-HT positively shifts the activation curve for the Ih and reduces the time constant for Ih activation. A, Sample current traces from a fusiform cell before and after applying 5-HT. Currents were evoked with a series of 5 s voltage steps from −120 to −50 mV, in 5 mV increments, from a holding potential of −60 mV, and followed by a test pulse to −75 mV. B, Mean normalized tail currents are plotted as a function of voltage steps and fit with the Boltzmann equation (n = 7). Tail currents were measured at −75 mV in the presence of Ba2+ to eliminate the contamination of Kir. C, Pooled data showing the effects of 5-HT on V1/2. Open symbols represent V1/2 of individual neurons, and filled symbols represent the mean of V1/2. D, Superimposition of current traces evoked by 10 s steps to −80 and −90 mV from a holding potential of −60 mV before and after applying 5-HT. E, Pooled data of time constants for Ih activation in the absence and presence of 5-HT (n = 4) at two voltages. Error bars are ± SEM.