Figure 4.
A dominant INCX over ICaL CDI imposes a positive [Ca]i-APD feedback and underlies bistability. A. APD map shows two discontinuous branches (red). Intersection of identity line (APDn=APDn-1) denotes two stable states (green dots). B. Attenuating the positive feedback between APD and [Ca]i by decreasing GNCX (not JNCX) progressively suppresses bistability. C. EAD alone (without positive [Ca]i-APD feedback by setting GNCX to 0) fails to produce bistability in either periodic 1 EAD (cyan) or irregular EADs (pink). For details see Supplemental Material, Figs. S5B and C.