Figure 7. SNAP potentiates the muscarinic activation of the muscarinic-activated K⁺ current, I_K,ACh, in rat atrial myocytes.

A, an atrial myocyte was first exposed to control potassium-rich solutions, and superfusion with SNAP (1 nm, 1 μm) or ACh (3 μm) was performed as indicated by the lines. I_K,ACh was measured at 0 mV (•) or −120 mV (▪) from a holding potential of −50 mV. B, same as in A, except that SNAP (1 pm, 1 nm, 1 μm) was applied in the presence of ACh (2 nm). Traces were recorded at the times indicated by the corresponding letters on the main graphs. The dotted lines indicate the zero-current level.