Figure 5.

Effects of M₃ mAChR subtype-selective antagonists on the pilocarpine-induced K⁺ current in canine atrial myocytes. Currents were elicited in the presence of 10 μM pilocarpine, with voltage protocols same as described in Figure 4. (A) A family of traces recorded before drug application, the K⁺ current induced in the presence of pilocarpine (10 mM), and inhibition of the currents by 4DAMP (2 nM). (B) Current density-voltage relationship of baseline current and after exposure of cells to 4DAMP at various concentrations indicated. Shown are averaged data from a total of eight cells. ^*P<0.05, ^**P<0.01, and ^***P<0.001 comparison between pilocarpine and pilocarpine + 4DAMP. (C) Per cent decreases in the pilocarpine-induced K⁺ current by 4DAMP (2 and 10 nM, n=8), 4DAMP mustard (4 and 20 nM, n=4), and p-F-HHSiD (20 and 200 nM, n=5), respectively. ^*P<0.05 without antagonist vs with antagonist.