Figure 4.

Pilocarpine induction of a novel K⁺ current via stimulation of M₃ receptors in isolated single guinea-pig atrial myocytes. Currents were elicited by 2 s pulses to potentials ranging from −40 to +50 mV with 10 mV increment followed by a 1 s step to −30 mV. Voltage steps were delivered from a holding potential (HP) of −50 mV at an interpulse interval of 5 s. (A) Analogue data showing current induction by pilocarpine (10 μM) and suppression by 4DAMP (2 nM, an M₃-selective antagonist). (B) I-V relationships under control conditions, in the presence of pilocarpine and after co-application of pilocarpine and 4DAMP (2 nM). (C) Examples showing the inhibitory effects of p-F-HHSiD (20 nM, an M₃-selective antagonist) on pilocarpine-induced K⁺ currents. Calibration same for A and C. (D) I-V relationships under control conditions, in the presence of pilocarpine and after co-application of pilocarpine and p-F-HHSiD (20 nM). Data shown are mean±s.e.mean from four cells.