Figure 3. Diltiazem binds to the extracellular side of the 5-HT₃ receptor.

Sample traces showing responses to extracellular application of 5-HT (30 μm, filled bar) with or without 100 μm diltiazem (open bar) co-applied externally with 100 μm diltiazem included in the patch pipette solution. A delay of 5 min was allowed after the whole-cell configuration had been established to allow complete dialysis of cell contents. Results are from a single experiment from one cell, and are typical of three experiments on different cells. The example shown was chosen to emphasise the difference in the time course of the response between control and diltiazem-modified responses, and the kinetics of the decay of the control response are within the range observed for other control responses.