Figure 1. Effects of serotonin on membrane potential and input resistance.

A, the downward deflections in the upper trace represent the changes in membrane potential during negative current pulses. Following 5-HT application, there was a small hyperpolarization which was associated with a decrease in the input resistance, as shown in the lower traces. However, this effect of serotonin was only observed in one-third of the cells, and the amplitudes of the hyperpolarization were quite small (see Results). B summarizes the concentration dependency of the reduction in input resistance in 6 cells (out of the one-third of cells which showed a hyperpolarization following the application of 5-HT).