Induction of constitutively active acetylcholine-activated K+ current, CA IKACh, in human AF. Single-channel IK1 and CA IKACh currents (A) and mean (±standard error) open probabilities (B), recorded at −120 mV in atrial cells from patients in SR (open symbols) and AF (solid symbols). *P <.05 versus SR. C: Potential signaling mechanism of increased CA IKACh in AF. In SR, IKACh may require channel phosphorylation by calmodulin-dependent PK II (CaMKII), PKG, and PKC.12 In AF, CA IKACh may result from upregulation of PKCϵ.12 Panels A and B are based on data in reference 10 with permission from Lippincott Williams & Wilkins.