Fig. 7.

Muscarinic receptor agonist carbachol does not affect the voltage-step induced steady-state BK currents upon pharmacological inhibition of all known cellular sources of Ca²⁺ for BK channel activation in freshly isolated rat DSM single cells. A: representative voltage-clamp recordings illustrating that 1 μM carbachol did not affect the steady-state BK currents at depolarization voltages from −40 to +80 mV. B: current-voltage relationship curve illustrating the lack of carbachol effect on the steady-state BK currents (n = 7, N = 6; P > 0.05). Steady-state BK currents were recorded in the presence of 30 μM ryanodine, 100 nM thapsigargin, and 1 μM nifedipine to block the ryanodine receptors (RyRs), sarcoplasmic reticulum (SR) Ca²⁺-ATPase, and L-type voltage-dependent Ca²⁺ channels, respectively.