Figure 1. Effects of 5-HT.

A, whole-cell current-clamp recording of spontaneous activity of a dorsal vagal neurone (DVN). Bath-application of 5-HT (20 μm) for 2 min (filled bar) causes a reversible, small depolarization and concomitant increase in spontaneous action potential firing. B, in voltage clamp, 5-HT reduces the standing outward current (I_SO) at −20 mV command voltage. C, this effect is completely blocked by prior application of the 5-HT₂ receptor antagonist ketanserin (1 μm). Note the slow recovery of the 5-HT inhibition of I_SO after washout of ketanserin, and the rundown of I_SO over the course of the recording. D, mean effects of 5-HT and ketanserin in recordings similar to those shown in B and C; ‘wash’ indicates the current after removal of 5-HT immediately prior to application of ketanserin. The difference between the ‘control’ and ‘wash’ bar, which is not statistically significant, reflects the rundown of I_SO prior to ketanserin treatment. Number of cells (n) is given above the bars. **P < 0.01 versus control (unpaired t test). E, representative current–voltage relation (I–V) obtained from a DVN in the presence and absence of 5-HT (20 μm), and I–V for the 5-HT-inhibited current (I_control−I_5-HT). This current is well described by the Goldman-Hodgkin-Katz (GHK) current equation (dashed line).